Introduction

OHAUS, a renowned brand in the laboratory instrumentation sector, is celebrated for its MB series moisture analyzers, which are recognized for their efficiency, reliability, and cost-effectiveness. Among them, the MB45 model stands out as an advanced product within the series, specifically tailored for industries such as pharmaceuticals, chemicals, food and beverage, quality control, and environmental testing. Leveraging cutting-edge halogen heating technology and a precision weighing system, the MB45 is capable of rapidly and accurately determining the moisture content of samples. This comprehensive user guide, based on the product introduction and user manuals of the OHAUS MB45 Halogen Moisture Analyzer, aims to assist users in mastering the instrument’s usage from understanding its principles to practical operation and maintenance. The guide will adhere to the following structure: principles and features of the instrument, installation and simple measurement, calibration and adjustment, operation methods, maintenance, and troubleshooting. The content strives to be original and detailed, ensuring users can avoid common pitfalls and achieve efficient measurements in practical applications. Let’s delve into the details step by step.

1. Principles and Features of the Instrument

1.1 Instrument Principles

The working principle of the OHAUS MB45 Halogen Moisture Analyzer is based on thermogravimetric analysis (TGA), a classical relative measurement method. In essence, the instrument evaporates the moisture within a sample by heating it and calculates the moisture content based on the weight difference before and after drying. The specific process is as follows:

• Initial Weighing: At the start of the test, the instrument precisely measures the initial weight of the sample. This step relies on the built-in high-precision balance system to minimize errors.
• Heating and Drying: Utilizing a halogen lamp as the heat source, the analyzer generates uniform infrared radiation heating, which is 40% faster than traditional infrared heating. The heating element, designed with a gold-reflective inner chamber, evenly distributes heat to prevent local overheating that could lead to sample decomposition. The temperature can be precisely controlled between 50°C and 200°C, with increments of 1°C.
• Real-Time Monitoring: During the drying process, the instrument continuously monitors changes in the sample’s weight. As moisture evaporates, the weight decreases until a preset shutdown criterion is met (e.g., weight loss rate falls below a threshold).
• Moisture Content Calculation: The moisture percentage (%Moisture) is calculated using the formula: Moisture% = [(Initial Weight – Dried Weight) / Initial Weight] × 100%. Additionally, the analyzer can display %Solids, %Regain, weight in grams, or custom units.

The advantage of this principle lies in its relative measurement approach: it does not require absolute calibration of the sample’s initial weight; only the difference before and after drying is needed to obtain accurate results. This makes the MB45 particularly suitable for handling a wide range of substances, from liquids to solids, and even samples with skin formation or thermal sensitivity. Compared to the traditional oven method, thermogravimetric analysis significantly reduces testing time, typically requiring only minutes rather than hours. Moreover, the built-in software algorithm of the instrument can process complex samples, ensuring high repeatability (0.015% repeatability when using a 10g sample).

In practical applications, the principle also involves heat transfer and volatilization kinetics. The “light-speed heating” characteristic of halogen heating allows the testing area to reach full temperature in less than one minute, with precision heating software gradually controlling the temperature to avoid overshooting. Users can further optimize heating accuracy using an optional temperature calibration kit.

1.2 Instrument Features

As a high-end model in the MB series, the OHAUS MB45 integrates multiple advanced features that set it apart from the competition:

• High-Performance Heating System: The halogen heating element is durable and provides uniform infrared heating. Compared to traditional infrared technology, it starts faster and operates more efficiently. The gold-reflective inner chamber design ensures even heat distribution, reducing testing time and enhancing performance.
• Precision Weighing: With a capacity of 45g and a readability of 0.01%/0.001g, the instrument offers strong repeatability: 0.05% for a 3g sample and 0.015% for a 10g sample. This makes it suitable for high-precision requirements, such as trace moisture determination in the pharmaceutical industry.
• User-Friendly Interface: Equipped with a 128×64 pixel backlit LCD display, the analyzer supports multiple languages (English, Spanish, French, Italian, German). The display provides rich information, including %Moisture, %Solids, weight, time, temperature, drying curve, and statistical data.
• Powerful Software Functions: The integrated database can store up to 50 drying programs. It supports four automatic drying programs (Fast, Standard, Ramp, Step) for easy one-touch operation. The statistical function automatically calculates standard deviations, making it suitable for quality control. Automatic shutdown options include three pre-programmed endpoints, custom criteria, or timed tests.
• Connectivity and Compliance: The standard RS232 port facilitates connection to printers or computers and supports GLP/GMP format printing. The instrument complies with ISO9001 quality assurance specifications and holds CE, UL, CSA, and FCC certifications.
• Compact Design: Measuring only 19×15.2x36cm and weighing 4.6kg, the analyzer fits well in laboratory spaces with limited room. It operates within a temperature range of 5°C to 40°C.
• Additional Features: Built-in battery backup protects data; multiple display modes can be switched; custom units are supported; a test library allows for storing, editing, and running tests; and statistical data tracking is available.
• Accessory Support: Includes a temperature calibration kit, anti-theft device, sample pan handler, 20g calibration weight, etc. Accessories such as aluminum sample pans (80 pieces) and glass fiber pads (200 pieces) facilitate daily use.

These features make the MB45 suitable not only for pharmaceutical, chemical, and research fields but also for continuous operations in food and beverage, environmental, and quality control applications. Its excellent repeatability and rapid results (up to 40% faster) enhance production efficiency. Compared to the basic model MB35, the MB45 offers a larger sample capacity (45g vs. 35g), a wider temperature range (200°C vs. 160°C), and supports more heating options and test library functions.

In summary, the principles and features of the MB45 embody OHAUS’s traditional qualities: reliability, precision, and user orientation. Through these technologies, users can obtain consistent and accurate results while streamlining operational processes.

2. Installation and Simple Measurement of the Instrument

2.1 Installation Steps

Proper installation is crucial for ensuring the accuracy and safety of the OHAUS MB45 Moisture Analyzer. Below is a detailed installation guide based on the step-by-step instructions in the manual.

• Unpacking and Inspection: Open the packaging and inspect the standard equipment: the instrument body, sample pan handler, 20 aluminum sample pans, glass fiber pads, specimen sample (absorbent glass fiber pad), draft shield components, heat shield, power cord, user manual, and warranty card. Confirm that there is no damage; if any issues are found, contact the dealer.
• Selecting a Location: Place the instrument on a horizontal, stable, and vibration-free workbench. Avoid direct sunlight, heat sources, drafts, or magnetic field interference. The ambient temperature should be between 5°C and 40°C, with moderate humidity. Ensure there is sufficient space at the rear for heat dissipation (at least 10cm). If moved from a cold environment, allow several hours for stabilization.
• Installing the Heat Shield, Draft Shield, and Sample Pan Support: Open the heating chamber cover and place the heat shield (circular metal plate) at the bottom of the chamber. Install the draft shield (plastic ring) to prevent airflow interference. Then, insert the sample pan support (tripod) and ensure stability.
• Leveling the Instrument: Use the front level bubble and adjustable feet to adjust the level. Rotate the feet until the bubble is centered to ensure repeatable results.
• Connecting the Power Supply: Plug the power cord into the socket at the rear of the instrument and connect it to a 120V or 240V AC, 50/60Hz power source. Warning: Use only the original power cord and avoid extension cords. Before the first use, ensure the voltage matches.
• Powering On: Press the On/Off button, and the display will illuminate. After self-testing, the instrument enters the main interface. If stored in a cold environment, allow time for预热 (warm-up) and stabilization.

After installation, it is recommended to perform a preliminary check: close the lid to ensure no abnormal noises; test the balance stability.

2.2 Simple Measurement Steps

After installation, you can proceed with a simple measurement to familiarize yourself with the instrument. Use the provided specimen sample (glass fiber pad) for the test.

• Preparing the Sample: Take approximately 1g of the specimen sample and evenly place it in an aluminum sample pan. Cover it with a glass fiber pad to prevent liquid splashing.
• Entering the Test Menu: Press the Test button to enter the default settings: Test ID as “-DEFAULT-“, temperature at 100°C, and time at 10:00 minutes.
• Placing the Sample: Open the cover and use the sample pan handler to place the sample pan inside. Close the cover to ensure a seal.
• Starting the Measurement: Press the Start/Stop button. The instrument begins heating and weighing. The display shows real-time information such as time, temperature, and moisture%.
• Monitoring the Process: Observe the drying curve. The initial weight is displayed, followed by the current moisture content (e.g., 4.04%) during the process. Press the Display button to switch views: %Moisture, %Solids, weight in grams, etc.
• Ending the Measurement: Once the preset time or shutdown criterion is reached, the instrument automatically stops. A beep sounds to indicate completion. The final result, such as the moisture percentage, is displayed.
• Removing the Sample: Carefully use the handler to remove the hot sample pan to avoid burns. Clean any residue.

This simple measurement typically takes 8-10 minutes. Through this process, users can understand the basic workflow: from sample preparation to result reading. Note: The first measurement may require parameter adjustments to match specific samples.

3. Calibration and Adjustment of the Instrument

3.1 Weight Calibration

Weight calibration ensures the accuracy of the balance. Although not strictly necessary for moisture determination, it is recommended to perform it regularly.

• Preparation: Use a 20g external calibration weight (an optional accessory). Ensure the instrument is level and the sample chamber is empty.
• Entering the Menu: Press the Setup button and select “Weight Calibration.”
• Process: Close the cover and press Enter to begin. When “Place 0g” is displayed, ensure the pan is empty; then, when “Place 20g” is shown, place the calibration weight on the pan. The instrument automatically calibrates and displays success or failure.
• Completion: Press Display to return to the main interface. If calibration fails, check for weight or environmental interference.

After calibration, print a report (if GLP is enabled) to record the date, time, and results.

3.2 Temperature Calibration

Temperature calibration uses an optional temperature calibration kit to ensure heating accuracy.

• Preparation: The kit includes a temperature probe. Allow the instrument to cool for at least 30 minutes.
• Entering the Menu: Navigate to Setup > “Temperature Calibration.”
• Process: Insert the probe and press Enter. The instrument heats to a preset temperature (e.g., 100°C), and the probe reading is compared to the instrument display. Adjust the deviation and press Enter to confirm.
• Multi-Point Calibration: Calibrate multiple temperature points (50-200°C) if needed.
• Completion: The display indicates success. Perform regular calibration (monthly or after frequent use).

3.3 Other Adjustments

• Language Settings: Navigate to Setup > Language to select English or other supported languages.
• Buzzer Volume: Adjust the buzzer volume under Setup > Beeper to Low/High/Off.
• Time and Date: Set the time and date format under Setup > Time-Date.
• Display Contrast and Brightness: Adjust the display visibility under Setup > Adjust Display.
• RS232 Settings: Configure the baud rate, parity, etc., under Setup > RS232.
• Printing and GLP: Enable automatic printing under Setup > Print/GLP.
• Factory Reset: Restore default settings under Setup > Factory Reset.

These adjustments optimize the user experience and ensure the instrument meets specific needs.

4. Operation of the Instrument

4.1 Operation Concepts

The MB45 is operated through the front panel buttons and menus. The main menu includes Setup (settings) and Test (testing). The test menu allows for customizing parameters such as Test ID, drying curve, temperature, shutdown criteria, result display, custom units, target weight, and print interval.

4.2 Entering a Test ID

Press Test > Test ID and input an alphanumeric ID (e.g., sample name).

4.3 Setting the Drying Curve

Choose from Standard (minimal overshoot), Fast (rapid heating), Ramp (controlled slope), or Step (three-step temperature).

4.4 Setting the Drying Temperature

Select a temperature between 50°C and 200°C, with increments of 1°C. Choose a temperature suitable for the sample to avoid decomposition.

4.5 Choosing Shutdown Criteria

• Manual: Press Stop to halt the test.
• Timed: Set a duration between 1 and 120 minutes.
• Automatic: Select A30/A60/A90 (weight loss rate < threshold/second).
• Automatic Free: Customize the weight loss rate.

4.6 Result Display

Choose to display %Moisture, %Solids, %Regain, weight in grams, or custom units.

4.7 Custom Units

Define formulas, such as the moisture/solids ratio.

4.8 Target Weight and Print Interval

Set a target weight prompt; configure the print interval between 1 and 120 seconds.

4.9 Saving and Running Tests

Save up to 50 test programs in the library; run a test by pressing Start.

4.10 Running Mode Display

View real-time curves and statistical data during operation.

4.11 Using the Library

Edit and lock test programs for consistent testing.

When operating the instrument, prioritize safety: wear gloves to avoid burns and optimize sample preparation for the best results.

5. Maintenance and Troubleshooting of the Instrument

5.1 Maintenance

Regular maintenance extends the instrument’s lifespan:

• Cleaning: After disconnecting the power, use a soft cloth to wipe the exterior. Use compressed air to blow dust out of the interior. Avoid introducing liquids.
• Replacing Fuses: Access the fuse box at the rear and replace fuses with the same specifications.
• Resetting Thermal Overload: If heating fails, press the reset button at the rear to restore functionality.
• Storage: Store the instrument in a dry, room-temperature environment.

5.2 Common Faults and Solutions

• Black Display Screen: Check the power supply and fuses; contact service if necessary.
• Prolonged Measurement Time: Adjust the shutdown criteria or drying curve.
• Inaccurate Results: Calibrate the weight and temperature; review sample preparation.
• Error Detection: The display shows error codes; refer to the manual to restart or seek service.
• Other Issues: If there is no weight change in the sample, clean the balance; if overheating occurs, check ventilation.

If issues persist, contact OHAUS service for assistance.

Conclusion

This comprehensive guide equips users with a thorough understanding of the OHAUS MB45 Halogen Moisture Analyzer. Users are encouraged to apply this knowledge in practice and optimize their testing processes for the best results.

Introduction

The 475DSP series gaussmeter (hereinafter referred to as the 475DSP gaussmeter), developed by Lake Shore Cryotronics, is a precision magnetic field measurement device that utilizes digital signal processing (DSP) technology to achieve high-accuracy detection of magnetic flux density and magnetic field strength. This equipment is suitable for various applications, including materials science, electromagnetism research, and industrial magnetic field monitoring. This guide is compiled based on the Model 475 User Manual (Revision 2.4, June 10, 2019) and covers four core modules: principles and characteristics, standalone operation and computer software integration, calibration and maintenance, and troubleshooting. It aims to guide users in safely and effectively utilizing the equipment. Note: If the device model or firmware version differs, please consult the latest resources on the Lake Shore website to ensure compatibility.

The guide adopts a hierarchical structure, first analyzing the basic principles of the device, then detailing the operation methods, followed by discussing maintenance strategies, and finally addressing potential issues. Through this guide, users can progress from basic introduction to advanced applications.

1. Principles and Characteristics of the Gaussmeter

1.1 Overview of Principles

The 475DSP gaussmeter operates based on the Hall effect, an electromagnetic phenomenon where a voltage perpendicular to both the current and magnetic field is generated when a current-carrying conductor is placed in a magnetic field. The magnitude of this voltage is directly proportional to the magnetic field strength. The device captures this voltage through a Hall probe and amplifies and converts it via internal circuitry to output magnetic field readings.

Unlike conventional analog instruments, the 475DSP integrates a DSP module to digitize analog signals for advanced processing, including noise suppression and algorithm optimization. The main system components include:

• Data Acquisition Mechanism: Continuous magnetic field signals are sampled and converted into digital sequences. The A/D converter collects data at a high frequency (e.g., dozens of times per second in DC mode) to ensure the capture of dynamic changes. The sampling theorem is followed to avoid frequency aliasing.
• DSP Core Operations: The processor performs filtering, spectral analysis (e.g., Fourier transforms for AC RMS calculations), and error correction. It considers the effects of quantization error and thermal noise to maintain measurement stability.
• Mode-Specific Principles:
  • DC Measurement: For constant or low-frequency magnetic fields, average filtering is used to eliminate random interference. Zero-field calibration utilizes a dedicated cavity to offset drift.
  • Root Mean Square (RMS) Measurement: Calculates the true RMS value of periodic AC fields, suitable for non-sinusoidal waves. Supports wide-band analysis with a frequency limit up to several kHz.
  • Peak Capture: Detects transient peaks, supporting both positive and negative polarities and pulse/continuous modes. High sampling rates (e.g., tens of thousands of Hz) are suitable for rapid pulse fields.
• Units and Conversion: Conversion between magnetic flux density B (units: Gauss (G) or Tesla (T)) and magnetic field strength H (Ampere/meter (A/m) or Oersted (Oe)) is based on the permeability relationship. In non-magnetic media, B ≈ μ₀H.
• Sensor Details: The Hall element has a small sensitive area and must be orthogonal to the magnetic field. Probe types vary, such as axial or transverse, with attention to polarity reversal and mechanical protection.

1.2 Characteristics Analysis

The 475DSP gaussmeter stands out with its advanced design, integrating precision, convenience, and durability. The following analysis covers performance, accessories, interface, and specifications:

• Performance Highlights:
  • Multi-Mode Support: DC, RMS, and peak modes, with a range from nanogauss to hundreds of kilogauss.
  • Precision Enhancement: ±0.05% reading accuracy in DC mode, with an RMS frequency response up to 20 kHz.
  • Intelligent Functions: Auto-ranging, peak locking, deviation comparison, and threshold alarms.
  • Environmental Adaptability: Built-in temperature monitoring with automatic compensation for thermal drift (<0.01%/°C).
• Accessory Features:
  • Probe Variety: High-precision (HST), sensitive (HSE), and extreme field (UHS) probes.
  • Memory Chips: Probe EEPROMs record calibration parameters for seamless integration.
  • Cable Extension: Supports cables up to 30 meters while maintaining signal integrity.
  • Custom Components: Bare Hall sensors for integrated applications, with resistance ranges of 500-1500 Ω and sensitivities of 0.05-0.15 mV/G.
• Interface and Connectivity:
  • Display System: Color LCD screen with dual-line display of field values and auxiliary information (e.g., frequency). Brightness is adaptive.
  • Control Panel: Full-function keyboard supporting shortcuts and menu navigation.
  • Communication Ports: GPIB (IEEE-488) and serial RS-232 for data transmission.
  • Output Options: Multiple analog voltages (±5 V or ±12 V) and relay control.
  • Indicator Lights: Status LEDs indicate operation modes.
• Technical Specifications:
  • Input: Single-channel Hall input with temperature compensation.
  • Accuracy Indicators: RMS ±0.5% (100 Hz-1 kHz), peak ±1.5%.
  • Environmental Adaptability: Operating temperature range of -10°C to 60°C, humidity <80%.
  • Power Supply: Universal AC 90-250 V, power consumption <20 W.
  • Physical Dimensions: 250 mm wide × 100 mm high × 350 mm deep, weighing approximately 4 kg.
  • Compliance: CE certification, Class A EMC, NIST traceable.
  • Warranty Policy: 3-year warranty from the shipping date, covering manufacturing defects (excluding abuse).
• Additional Advantages:
  • Firmware Reliability: Although software limitations may exist, results are emphasized through dual verification.
  • Safety Design: Grounding requirements and anti-static measures.
  • EMC Optimization: Shielding recommendations for laboratory use to avoid RF interference.
    These characteristics make the 475DSP suitable for precision magnet calibration and electromagnetic shielding testing, providing robust solutions.

2. How to Use the Gaussmeter Independently and via Computer Software

2.1 Standalone Usage Guide

The 475DSP gaussmeter is designed for user-friendliness and supports standalone operation without external devices. The following covers steps from installation to advanced applications.

2.1.1 Installation Preparation

• Unpacking Inspection: Confirm that the package includes the host unit, power adapter, optional probes, and documentation.
• Rear Panel Interfaces: Connect the power supply (90-250 V), probe port (D-sub 15-pin), and I/O expansion (including analog output and relay).
• Power Configuration: Install an appropriate fuse (1 A slow-blow) and use a grounded socket. The power switch is located on the rear.
• Probe Installation: Insert the probe, which is automatically recognized by the EEPROM. If not detected, the screen prompts “Probe Missing.”
• Mechanical Considerations: The probe’s bending radius is limited to 3 cm to avoid physical stress.
• Installation Options: Supports desktop or rack mounting using dedicated brackets.

2.1.2 Basic Operations

• Startup: Upon power-on, the device performs a self-test and displays firmware information. It defaults to DC mode.
• Screen Interpretation: The main line displays the magnetic field value, while the auxiliary line shows temperature or frequency. The unit switching key supports G/T/A/m/Oe.
• Key Functions: Shortcut keys switch modes, long presses activate submenus, arrows navigate, and numbers input parameters.
• Unit Adjustment: A dedicated key cycles through magnetic field units.
• DC Operation: Select DC mode and set auto/manual range. Filter levels include precision (slow), standard, and fast. Zero calibration is performed by placing the probe in a zero cavity and pressing the zero key. Peak mode locks extreme values (absolute or relative). Deviation sets a reference for comparison.
• RMS Operation: Switch to RMS mode and configure bandwidth (wide/narrow). Displays the RMS value and frequency. Alarm thresholds can be set.
• Peak Operation: Select peak mode and pulse/periodic submodes. Captures instantaneous high and low peaks, supporting reset.
• Temperature Function: Displays the probe temperature in real-time (°C/K) and enables compensation.
• Alarm System: Defines upper and lower limits and activates buzzers or external signals.
• Output Control: Configures analog channel proportions and relay linkage with alarms.
• Locking Mechanism: Password-protects the keyboard (default password: 456).
• Reset: A combination key restores factory settings (retaining calibration).

2.1.3 Advanced Standalone Functions

• Probe Configuration: Resets compensation or programs custom probes in the menu.
• Cable Programming: Uses a dedicated cable to input sensitivity.
• Environmental Considerations: For indoor use, avoid high RF areas, with an altitude limit of 3000 m.
  Standalone mode is ideal for portable measurements and offers intuitive operation.

2.2 Usage via Computer Software

The 475DSP is equipped with standard interfaces to support remote control and automation.

2.2.1 Interface Preparation

• GPIB Setup: Address range 1-31 (default 5), with terminators LF or EOI.
• Serial Port Parameters: Baud rate 1200-19200 bps (default 19200), no parity. Use a DB-9 connector.
• Mode Switching: The remote mode is indicated by LEDs. Press the local key to return.

2.2.2 Software Integration

• Status Monitoring: Utilizes event registers to query operational status, such as *STB?.
• Command Library: System commands like *RST for reset and queries like FIELD? to read values. MODE sets the mode.
• Programming Examples: Configures interfaces in Python or C++ and sends commands like *IDN? to confirm the device.
• Service Requests: Enables SRQ interrupts for synchronous data.
• Serial Protocol: Commands end with CR, and responses are simple to parse.
• Compatible Software: Supports NI LabVIEW drivers; consult Lake Shore for details.
• Debugging Tips: Verify connection parameters and check cables or restart if there is no response.
  Computer mode is suitable for batch data collection, such as plotting magnetic field maps with scripts.

3. How to Calibrate, Debug, and Maintain the Gaussmeter

3.1 Calibration and Debugging

Regular calibration maintains accuracy, and it is recommended to have the device calibrated annually by Lake Shore using NIST standards.

3.1.1 Required Tools

• Computer with communication software.
• High-precision multimeter (e.g., Fluke 87).
• Resistance standards (10 kΩ-1 MΩ, 0.05% precision).
• Zero-field cavity.

3.1.2 Calibration Process

• Gain Adjustment: Input analog voltage and use the CALGAIN command to calculate the factor (actual/expected).
• Zero Offset: Use the CALZERO command to clear the offset.
• Temperature Calibration: Measure resistance with varying currents and update compensation coefficients.
• Output Verification: Set the voltage range, measure, and fine-tune the offset.
• Storage: Use the CALSTORE command to save to non-volatile memory.
• Debugging Steps: Perform zero-field tests to verify the baseline, enable compensation to check stability, simulate thresholds to confirm alarms, and input values in deviation mode to test calculations.
• Probe Handling: Calibrate cables integrally and input custom sensitivity (mV/G).

3.1.3 Maintenance and Care

• Daily Cleaning: Wipe dust with a soft cloth, avoiding solvents. Store between -30°C and 70°C.
• Probe Protection: Protect from impacts and perform regular zero calibrations.
• Power Supply Check: Replace fuses and ensure stable voltage.
• EMC Practices: Use short cable routes and separate signals.
• Firmware Management: Consult the manufacturer before updating the firmware.
• Warranty Reminder: Modifications invalidate the warranty; exclude disasters.
  Regular maintenance ensures long-term reliability.

4. What are the Faults of the Gaussmeter and How to Address Them

4.1 Common Fault Classifications

Faults can be categorized into device, user, and connection types, with error codes displayed on the screen.

4.1.1 Device Faults

• Probe Not Detected: Loose connection or faulty probe. Solution: Reconnect, check the cable. Replace if defective.
• Calibration Failure: Data corruption. Solution: Reset memory and recalibrate.
• Internal Communication Disruption: Hardware issue. Solution: Restart; if persistent, return for repair.
• Memory Error: EEPROM problem. Solution: Restore defaults and verify.
• Out of Range: Excessive magnetic field. Solution: Adjust the range or remove the source.
• Temperature Overload: Sensor overheating. Solution: Cool down and wait.

4.1.2 User Operation Faults

• Keyboard Lock: Password activated. Solution: Input the password to unlock.
• Invalid Command: Mode conflict. Solution: Switch to a compatible mode.
• Reading Fluctuations: Interference. Solution: Enhance filtering and shielding.

4.1.3 Connection Faults

• GPIB Unresponsive: Configuration error. Solution: Check the address and use *CLR to clear.
• Serial Port Error: Parameter mismatch. Solution: Match the baud rate and check the line.
• Interrupt Failure: Register not set. Solution: Enable *SRE.

4.1.4 General Troubleshooting Steps

• Steps: Power off and restart, check the manual for error codes, and press the clear key.
• Service: Provide the model number.
• Prevention: Follow grounding specifications and avoid use in explosive areas.
• Software Issues: Recheck abnormal readings and avoid reverse engineering.
  Quick responses minimize downtime.

Conclusion

This guide provides a comprehensive overview of the application of the 475DSP gaussmeter, assisting users in optimizing their operations. Combining practical experience with the manual deepens understanding.

Introduction

The 455DSP series gaussmeter from Lake Shore Cryotronics is an advanced digital signal processing (DSP)-based magnetic field measurement instrument widely used in scientific research, industrial production, and quality control. Leveraging the Hall effect principle combined with modern DSP technology, it offers high-precision, wide-range magnetic field measurement capabilities. This user guide, based on the official manual (Model 455 Series, Revision 1.5), provides detailed instructions on principles and features, standalone and PC software operation, calibration and maintenance, and troubleshooting. It aims to help users operate the device efficiently and safely. Note: Ensure the model matches the manual during operation.

This guide is structured to first introduce core principles and advantages, then guide operation procedures, followed by maintenance and calibration, and finally analyze fault exclusion.

1. Principles and Features of the Gaussmeter

1.1 Principle Overview

The 455DSP gaussmeter is based on the Hall effect, a phenomenon where a current-carrying conductor in a magnetic field generates a transverse voltage. Specifically, when current flows through a Hall sensor (typically a semiconductor like indium arsenide) placed perpendicular to the current direction in a magnetic field, a Hall voltage proportional to the magnetic field strength is produced. This voltage is amplified and digitized to provide readings of magnetic flux density (B) or magnetic field strength (H).

The instrument employs digital signal processing (DSP) technology to convert analog signals into digital signals for processing, allowing for more precise filtering, compensation, and calculations compared to traditional analog gaussmeters. The system overview is as follows:

• Sampling Data System: While humans perceive the world through continuous analog signals, modern instruments use sampling systems to convert these signals into discrete digital samples. The 455DSP gaussmeter uses an analog-to-digital converter (A/D) to capture Hall voltage at a high sampling rate (e.g., up to 30 readings per second in DC mode), ensuring real-time responsiveness.
• DSP Processing: The DSP chip processes the sampled data, including digital filtering, Fourier transforms (for RMS and peak modes), and compensation algorithms. Limitations include the Nyquist theorem (sampling rate must be at least twice the signal frequency to avoid aliasing) and quantization noise (determined by A/D resolution).
• Measurement Mode Principles:
  • DC Mode: Suitable for static or slowly varying magnetic fields. Uses digital filters to smooth noise and provide high-resolution readings. Zero-point calibration eliminates offset using a zero-gauss chamber.
  • RMS Mode: Measures the effective value of periodic AC magnetic fields. Uses true RMS calculation to account for waveform distortion. Frequency range up to 1 kHz, supporting broadband or narrowband filtering.
  • Peak Mode: Captures peaks (positive/negative) of pulsed or periodic magnetic fields. Sampling rate up to 10 kHz, suitable for transient fields like electromagnetic pulses. Periodic mode continuously updates peaks, while pulse mode captures single events.
• Magnetic Flux Density vs. Magnetic Field Strength: Magnetic flux density (B) is the magnetic flux per unit area, measured in gauss (G) or tesla (T). Magnetic field strength (H) is the intensity generating the magnetic field, measured in amperes per meter (A/m). In vacuum or air, B = μ₀H (μ₀ is the vacuum permeability). The instrument can switch between unit displays.
• Hall Measurement Details: The Hall sensor has an active area (typically 0.5 mm × 0.5 mm), with polarity depending on the magnetic field direction, requiring the sensor to be perpendicular to the field. Probes include transverse and axial types, with a minimum bending radius (2.5 cm) to avoid damage.

1.2 Feature Analysis

The 455DSP gaussmeter integrates multiple innovative features that distinguish it from similar products. Below are detailed descriptions of its measurement, probe, display and interface, and specification features:

• Measurement Features:
  • Supports DC, RMS, and peak modes, covering a wide range from microgauss to 350 kG.
  • High resolution: 4¾ digits in DC mode, supports frequency measurement (1 Hz to 20 kHz) in RMS mode.
  • Auto-ranging (Autorange) and manual range selection for flexibility.
  • Max/min hold (Max Hold), relative measurement (Relative), and alarm functions enhance practicality.
  • Temperature measurement: Integrated temperature sensor compensates for probe thermal drift, improving accuracy.
• Probe Features:
  • Compatible with multiple probes: high-stability (HST), high-sensitivity (HSE), and ultra-high magnetic field (UHS).
  • Probe-embedded EEPROM stores serial number, sensitivity, and compensation data for plug-and-play functionality.
  • Supports temperature compensation to reduce thermal effect errors (typical <0.02%/°C).
  • Extension cables: Up to 100 feet with EEPROM calibration data.
  • Bare Hall generators: For custom applications, with specifications including input resistance (typical 600-1200 Ω) and output sensitivity (0.06-0.13 mV/G).
• Display and Interface Features:
  • Dual-line 20-character vacuum fluorescent display (VFD) with adjustable brightness (25%-100%).
  • LED indicators: For relative, alarm, and remote modes.
  • Keyboard: 22 full-travel keys supporting direct operation, hold, and data input.
  • Interfaces: IEEE-488 (GPIB) and RS-232 serial ports for remote control and data acquisition.
  • Analog outputs: Three channels (Analog Output 1-3), configurable as ±3V or ±10V, proportional to field value.
  • Relays: Two mechanical relays following alarm or manual control.
• Specification Parameters:
  • Input type: Single Hall sensor with temperature compensation.
  • DC accuracy: ±0.1% of reading ±0.005% full scale.
  • RMS accuracy: ±1% (50 Hz-400 Hz).
  • Peak accuracy: ±2%.
  • Temperature range: 0-50°C, stability ±0.03%/°C.
  • Power: 100-240 VAC, 50/60 Hz.
  • Dimensions: 216 mm wide × 89 mm high × 318 mm deep, weight 3 kg.
  • EMC compatibility: Meets CE Class A standards, suitable for laboratory environments.
  • Warranty: 3 years covering material and workmanship defects (excluding improper maintenance).
• Other Advantages:
  • Firmware limitations: Ensure accuracy but emphasize result verification.
  • Safety symbols: Include warnings, cautions, and grounding identifiers.
  • Certification: NIST-traceable calibration, compliant with electromagnetic compatibility directives.

These features make the 455DSP gaussmeter suitable for applications in low-temperature physics, magnetic material testing, and electromagnetic compatibility, providing reliable measurement solutions.

2. How to Use the Gaussmeter Independently and via PC Software?

2.1 Standalone Operation Guide

The 455DSP gaussmeter supports standalone operation without a PC for most measurement tasks. The following steps detail installation, basic operation, and advanced functions.

2.1.1 Installation and Preparation

• Unpacking: Check packaging integrity; accessories include the instrument, power cord, probe (optional), and manual.
• Rear Panel Connections:
  • Power input (100-240 V).
  • Probe input (15-pin D-type).
  • Auxiliary I/O (25-pin D-type, including relays and analog outputs).
• Power Setup:
  • Select voltage (100/120/220/240 V).
  • Insert fuse (0.5 A slow-blow).
  • Connect grounded power cord. Power switch located on the rear panel.
• Probe Connection:
  • Insert probe, ensuring EEPROM data is read. Displays “NO PROBE” if no probe is connected.
• Probe Handling:
  • Avoid bending probe stem (minimum radius 2.5 cm); do not apply force to the sensor. In DC mode, direction affects polarity.
• Rack Mounting: Optional RM-1/2 kit supports half-rack or full-rack mounting.

2.1.2 Basic Operation

• Power On: Press power switch; display initializes (firmware version). Defaults to DC mode.
• Display Definition:
  • Upper line: Field value.
  • Lower line: Temperature/frequency.
  • Units: G, T, A/m, Oe.
  • Brightness adjustment: Hold Display key, select 25%-100%.
• Keyboard Operation:
  • Direct keys (e.g., DC/RMS/Peak toggle).
  • Hold keys (e.g., zero).
  • Selection keys (s/t arrows) and data input.
• Unit Switching: Press Units key, select G/T or A/m/Oe.
• DC Mode:
  • Press DC key. Auto/manual range (press Select Range). Resolution and filtering: slow (high precision), medium, fast. Zero-point: insert zero-gauss chamber, press Zero Probe. Max Hold: press Max Hold, captures max/min (algebraic or amplitude). Relative: press Relative, use current field or setpoint. Analog output: proportional to field value.
• RMS Mode:
  • Press RMS key. Filter bandwidth: wide (DC-1 kHz) or narrow (15 Hz-10 kHz). Frequency measurement: displays dominant frequency. Reading rate: slow/medium/fast. Max Hold and relative similar to DC mode.
• Peak Mode:
  • Press Peak key. Configure periodic/pulse. Displays positive/negative peaks. Frequency measurement supported. Relative and reset available.
• Temperature Measurement: Automatically displays probe temperature (°C or K).
• Alarm:
  • Press Alarm, set high/low thresholds, internal/external mode. Buzzer optional.
• Relays:
  • Press Relay, configure manual or follow alarm.
• Analog Output 3:
  • Press Analog Output, modes: default, user-defined, compensation. Polarity: single/double. Voltage limit: ±10 V.
• Keyboard Lock:
  • Press Lock, enter code (123 default).
• Default Parameters:
  • Press Escape + Enter to reset EEPROM (does not affect calibration).

2.1.3 Advanced Standalone Operation

• Probe Management:
  • Press Probe Mgmt, clear zero-point or temperature compensation.
• User Programming Cable:
  • Connect HMCBL cable, press MCBL Program to program sensitivity.
• EMC Considerations:
  • Use shielded cables, avoid RF interference. Indoor use, altitude <2000 m.

Standalone operation is suitable for on-site rapid measurements, with a user-friendly interface.

2.2 Using PC Software for Operation

The 455DSP supports IEEE-488 and serial interfaces for remote control and data acquisition, requiring upper computer software like LabVIEW or custom programs.

2.2.1 Interface Setup

• IEEE-488:
  • Address 0-30 (default 4), terminator CR LF/LF CR/EOI. Press IEEE to set.
• Serial Port:
  • Baud rate (300-9600, default 9600), parity (none/odd/even). Connect DB-9.
• Remote/Local:
  • Remote mode LED illuminates; press Local to return to local mode.

2.2.2 Software Operation

• Status System:
  • Includes standard event register (ESR) and operation event register (OPST). Use ESE, ESR? to query.
• Command Summary:
  • CLS clears, IDN? identifies, *OPC completes. Measurement commands: RDGFIELD? reads field value, RDGMODE sets mode.
• Example Program:
  • Use Visual Basic or NI-488.2. Configure GPIB board, send commands like *IDN? to get ID.
• Programming Example:
  • Generate SRQ (service request), use *OPC to synchronize operations.
• Serial Port Messages:
  • End with , queries end with ?.
• LabVIEW Driver:
  • Lake Shore provides; consult availability.
• Troubleshooting:
  • Check address/baud rate, ensure terminator. If no response, restart or check cable.

PC operation is suitable for automated testing and data logging, such as analyzing magnetic field distributions with MATLAB.

3. How to Calibrate, Debug, and Maintain the Gaussmeter?

3.1 Calibration and Debugging

Calibration ensures measurement accuracy; recommended annually. Lake Shore provides NIST-traceable services.

3.1.1 Equipment Required

• PC with serial port software.
• Digital multimeter (DMM, e.g., Keithley 2000).
• Precision resistors (22.1 kΩ, 200 kΩ, etc., 0.1% precision).
• Zero-gauss chamber.

3.1.2 Gaussmeter Calibration

• Gain Calibration:
  • Use resistors to simulate Hall voltage. Send CALG command to set gain factor (GCF = expected/actual).
• Zero-Point Offset:
  • Use CALZ command.
• Temperature Measurement Calibration:
  • Excite current (10 μA, 100 μA, 1 mA), measure resistance, calculate GCF.
• Analog Output Calibration:
  • Set mode, measure voltage, adjust GCF and OCF.
• Save:
  • CALSAVE command stores to EEPROM.
• Debugging:
  • Zero-point probe: Insert into zero-cavity, press Zero Probe. Temperature compensation: Press Probe Mgmt to enable. Relative mode debugging: Setpoint verification for deviation. Alarm debugging: Simulate field value to check buzzer/relay. Probe calibration: Calibrate with extension cable. User programming: Input sensitivity (mV/kG).

3.1.3 Maintenance

• Daily Maintenance:
  • Keep clean, avoid dust. Storage temperature -20°C to 60°C.
• Probe Maintenance:
  • Avoid bending, collision. Regular zero-point checks.
• Power and Fuse:
  • Check voltage, replace 0.5 A fuse.
• EMC Maintenance:
  • Use shielded cables, short routes, avoid bundling different signals.
• Firmware Updates:
  • Consult Lake Shore; no strict deadline.
• Warranty Note:
  • Improper maintenance (e.g., modifying firmware) voids warranty.

Maintenance extends lifespan and ensures accuracy.

4. What are the Common Faults of the Gaussmeter and How to Handle Them?

4.1 Common Fault Classification

Faults are categorized into hardware, operational, and interface types. Error messages display on-screen.

4.1.1 Hardware Faults

• No Probe: Probe not connected or damaged. Handle: Check connection, reinsert. If damaged, replace.
• Invalid Calibration: Calibration data corrupted. Handle: Reset EEPROM, press Escape + Enter. Requires recalibration.
• Input Not Responding: Internal communication failure. Handle: Restart; if persistent, return for repair.
• EEPROM Error: Parameters default; recurrence indicates EEPROM defect. Handle: Reset, check calibration.
• Overload: Field exceeds range. Handle: Switch range or remove strong field.
• Temp Overload: Sensor exceeds range. Handle: Cool probe.

4.1.2 Operational Faults

• LOCKED: Keyboard locked. Handle: Input code to unlock.
• Illegal Operation: E.g., Max unavailable in peak mode. Handle: Configure mode.
• Measurement Unstable: Noise or interference. Handle: Enable filtering, shield environment.

4.1.3 Interface Faults

• IEEE-488: No response. Handle: Check address, terminator. Send *CLS to clear.
• Serial Port: Transmission error. Handle: Match baud rate, check parity. Verify TD/RD lines.
• SRQ Failure: Event register issue. Handle: Enable ESE bits, set SRE.

4.1.4 Handling Methods

• General Steps:
  • Restart instrument, check cables/power. Refer to error message, press Escape to clear.
• Return to Factory:
  • If persistent, provide serial number.
• Prevention:
  • Follow safety (e.g., grounding), avoid explosive environments.
• Firmware Issues:
  • Verify data if results abnormal; avoid modifying code.

Timely handling ensures reliable operation.

Conclusion

This guide comprehensively covers the use of the 455DSP gaussmeter, helping users progress from basic to advanced operations. For practical application, combine with the manual for experimentation.

1. Overview and Principle

The NEXTorr® Z 100 ND Float Pump is a hybrid ultra-high vacuum pump that combines a Non-Evaporable Getter (NEG) with a Sputter Ion Pump (SIP). The NEG element efficiently removes active gases such as H₂, CO, CO₂, O₂, and H₂O, while the ion pump handles inert gases (such as Ar) and methane, also providing a current signal that can be used as a pressure indication. The Z100 features compact size, low power consumption, and minimal magnetic interference, making it ideal for scanning electron microscopes and other sensitive equipment.

NEG works by chemically absorbing and dissolving gas molecules at room temperature, but it must first be activated at high temperature (about 400–500 °C for 1 hour) to remove the passivation layer. After activation, NEG continuously pumps at room temperature with virtually no power consumption. The ion pump operates by ionizing residual gas molecules under high electric and magnetic fields. Positive ions are accelerated to strike the cathode and become trapped. The “ND” (Noble Diode) design improves the pumping of inert gases.

2. Applications

• Ultra-high vacuum chambers in SEMs
• Compact research equipment with space constraints
• Systems sensitive to vibration and magnetic fields
• Environments with a significant inert gas background

3. Installation and Commissioning

3.1 Mechanical Installation

• Verify flange type and sealing surfaces are clean and free of scratches.
• Use copper gaskets or O-rings, tighten with proper torque.
• Avoid vacuum grease contamination, keep the pump inlet clean.
• Install away from strong magnetic fields of the electron optics.

3.2 Electrical Connection

• The ion pump requires a high-voltage power supply (typically 3–7 kV).
• The NEG requires heater/temperature control for activation.
• Ensure HV cables are securely locked and correct polarity is applied.

3.3 Initial Pump Down and Leak Check

• Use a forepump/turbo system to reach ≤10⁻⁶ mbar before activation.
• Perform helium leak detection to confirm no flange leakage.

3.4 NEG Activation

• Heat NEG under vacuum to 400–500 °C for about 1 hour.
• Monitor vacuum level and ion pump current during activation.
• Cool down to room temperature before normal operation.

3.5 Ion Pump Startup

• Once good vacuum is established and NEG is activated, gradually apply HV to start the ion pump.
• Monitor ion current decreasing trend as an indication of pressure.

4. Operation and Maintenance

• Use ion pump current as a proxy for chamber pressure.
• For long-term shutdown, fill chamber with dry nitrogen to prevent contamination.
• NEG can be reactivated several times but capacity will decrease gradually.
• Avoid hydrocarbons or oil vapors entering the vacuum system.

5. Common Failures and Troubleshooting

1. Slow pumping or cannot reach target pressure: Possible leaks, unactivated NEG, contamination, or poor conductance. → Leak check, re-activation, bakeout.
2. High ion pump current: Possible leaks, discharges, or wiring errors. → Inspect sealing, reduce HV, check wiring.
3. NEG performance decline: May be saturated or surface contaminated. → Re-activate or replace NEG.
4. HV discharges: May be due to insufficient vacuum or insulation issues. → Reduce HV, re-pump, clean cables.
5. Unstable readings: Ion current depends on gas composition. → Cross-check with independent gauges.

6. Integration with SEM

• Minimize Ar contamination from sample preparation.
• Control activation temperature within SEM chamber tolerance.
• Use ion pump current as interlock for SEM HV supply.
• Maintain strict cleanliness to prevent NEG contamination.

7. Safety Notes

• Ion pump power supply is high voltage; always power down and discharge before servicing.
• NEG activation involves high temperature; ensure insulation and thermal compatibility.
• Follow SEM manufacturer’s operational and safety guidelines.

8. Conclusion

The NEXTorr® Z 100 ND Float Pump combines the fast pumping speed of NEG with the full gas spectrum coverage of an ion pump. Its compact design, low power consumption, and long lifetime make it ideal for SEM and UHV applications. Proper installation, activation, and regular maintenance are essential to ensure stable long-term performance.