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| Home > Lake Shore Products > Magnetic Instruments & Sensors > Gaussmeters > Model 475 DSP Gaussmeter |
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Model 475 DSP Gaussmeter |
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 Back to Lake Shore Model 475 Gaussmeter product overview |
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| The power of DSP technology is demonstrated in the superior performance of the Model 475 in DC, RMS, and Peak measurement modes. |
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| DC Measurement Mode |
 Static or slowly changing fields are measured in DC mode, where the accuracy, resolution, and stability of the Model 475 are most evident. In this mode, the gaussmeter takes advantage of the internal auto zero function and probe linearity compen-sation to provide its best accuracy. Measurement resolution is enhanced by advanced signal processing capability, allowing users the choice of high reading rates to 100 readings per second or high resolution to 5¾ digits. The Model 475 also features front-end amplification specifically designed to complement DSP data acquisition, providing high stability and repeatability. That, along with probe temperature compensation, makes the Model 475 the most stable gaussmeter ever produced by Lake Shore, suiting it perfectly for demanding DC measurement applications such as field mapping and field control. |
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| RMS Measurement Mode |
 Periodic, AC fields are measured in RMS mode, which highlights the uniquely flexible filter functions of the Model 475. An overall RMS frequency range of 0.5 Hz to 50 kHz is offered by the gaussmeter. Selectable band-pass and lowpass filters allow users to reject unwanted signals and improve measurement performance. The exclusive Lake Shore Digital Signal Processing algorithms also free the Model 475 from the limitations of conventional RMS conversion hardware and provide better dynamic range, resolution, and frequency response than ever before. These improvements permit meaningful RMS field measurements with broad frequency content or in noisy environments. |
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| Peak Measurement Mode |
 Pulsed fields are measured in Peak mode, which is a natural extension of the high-speed data acquisition necessary for DSP operation. Fast instrument sample rates permit capture of positive and negative field pulses as narrow as 20 µs in width, which can be held for an unlimited length of time with no sag. This is ideal for most magnetizers and other fast pulse applications. For more moderate field changes, the Model 475 can process the captured data to create other features. The gaussmeter can be configured to follow the peak of a periodic waveform for evaluation of crest factor. The Model 475 can also be used to sample field changes at 1000 readings per second that can later be read over the interface to illustrate the shape of pulses or other waveforms. |
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| The Probe Connection |
The Model 475 is only half of the magnetic field measurement equation. For the complete solution, Lake Shore offers a full complement of standard and custom Hall effect probes in a variety of sizes and sensitivities.
Click here for complete details on properly selecting a Hall effect probe.
Click here for a complete listing of available probe models.  |
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| Advanced Features |
| The Model 475 combines hardware and firmware elements to create advanced features that facilitate automation and material analysis. |
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| Field Control |
| A built-in PI control algorithm turns the Model 475 into an essential building block for magnetic field control in electromagnet systems. It, along with a voltage-programmable magnet power supply, is all that is needed to control stable magnetic fields in an electro-magnet at the user specified setpoint. One of the built-in analog voltage outputs drives the program input of the power supply for either bipolar or unipolar operation. |
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| High Speed Data Transfer |
| The IEEE-488 interface can be set to send readings in binary format rather than the more common ASCII format. This reduces interface overhead, enabling real time reading rates up to 100 new readings per second. Temperature compensation is not available at the highest interface rate. |
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| Data Buffer |
| Internal memory provides storage for 1024 field readings in a data buffer. The buffer can be filled at high speed, up to
1000 readings per second, which is as much as ten times faster than the computer interface. Stored
readings can be retrieved over interface at slower speed and processed off-line. A trigger input can be used to initiate the data log sequence. Slower sample rates can be programmed if desired. |
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| Trigger In and Trigger Out |
| A TTL-level hardware trigger into the instrument can be used to initiate the data log sequence. A TTL-level hardware trigger out indicates when the instrument completes a reading, and can be used to synchronize other instruments in the system. An IEEE-488 software-based trigger can be used like the hardware trigger in.
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| Measurement Features |
| The Model 475 offers a variety of features to enhance the usability and convenience of the gaussmeter. |
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| Auto Range: In addition to manual range selection, the instrument automatically chooses an appropriate range for the measured field. Auto range works in DC and AC measurement modes. |
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Auto Probe Zero: Allows the user to zero all ranges for the selected measurement mode with the push of a key. |
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| Display Units: Field magnitude can be displayed in units of G, T, Oe, and A/m. |
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Max/Min Hold: The instrument stores the fully processed maximum and minimum DC or RMS field value. This differs from the faster peak capture feature that operates on broadband, unprocessed field reading information. |
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| Relative Reading: Relative feature calculates the difference between a live reading and the relative setpoint to highlight deviation from a known field point. This feature can be used in DC, RMS, or Peak measurement mode. |
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Instrument Calibration: Lake Shore recommends an annual recalibration schedule for all precision gaussmeters. Recalibrations are always available from the factory, but the Model 475 allows users to field calibrate the instrument if necessary. Recalibration requires a computer interface and precision low resistance standards of known value. |
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| Instrument Probe Features |
| The Model 475 has several capabilities that allow the best possible measurements with Lake Shore probes. These firmware-based features work in tandem with the probe’s calibration and programming to ensure accurate, repeatable measurements and ease of setup. Many of the features require probe characteristics that are stored in the probe connector’s non-volatile memory. |
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Probe Field Compensation: The Hall effect devices used in gaussmeter probes produce a near linear response in the presence of magnetic field. The small nonlinearities present in each individual device can be measured and subtracted from the field reading. Model 475 probes are calibrated in this way to provide the most accurate DC readings. |
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Probe Temperature Compensation: Hall effect devices show a slight change in sensitivity and offset with temperature. Probe temperature effects can be measured and subtracted out of field readings. A temperature sensor in the probe tip relays real time tempera-ture to the gaussmeter, enabling compensation. Although temperature effects contribute only a small fraction of the overall probe measurement accuracy, temperature compensation will often improve measurement and control stability. |
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| Probe Temperature Display: The gaussmeter can display the probe’s temperature in °C along with a field reading when using a probe that includes a temperature sensor. |
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Frequency Display: When operating in RMS mode, the gaussmeter can display the frequency of the measured AC field along with a field reading. |
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Probe Information: The gaussmeter reads the probe information on power up or any time the probe is changed to allow hot swapping of probes. Critical probe information can be viewed on the front panel and read over the computer interface to ensure proper system configuration. |
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Extension Cables: The complex nature of Hall effect measurements make it necessary to match extension cables to the probe when longer cables are needed. Keeping probes and their extensions from getting mixed up can become a problem when more than one probe is in use. The Model 475 alleviates most of the hassle by allowing users to match probes to extensions in the field. Stored information can be viewed on the front panel and read over the computer interface to ensure proper mating. |
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Hall Effect Generators (Magnetic Field Sensors): The Model 475 will operate with a discrete Hall effect generator when a suitable probe is not available. Users can program nominal sensitivity and serial number into an optional MCBL-6 blank connector to provide all gaussmeter functions except field and temperature compensation. If no sensitivity information is available, the Model 475 reverts to resistance measurement. |
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| Alarm and Relay |
High and low alarms are included in the instrument. Alarm actuators include display annunciator, audible beeper, and two relays. The relays can also be controlled manually for other system needs. |
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| Voltage Output 1 |
| The first voltage output gives access to amplified voltage signal directly from the probe. This voltage is corrected for the nominal sensitivity of the probe and provides the widest bandwidth of the three voltage outputs. In wideband AC mode, the signal can be viewed on an oscilloscope to observe the shape of AC fields. In peak mode, the output can be used to view a pulse shape or other characteristic of a momentary signal. Output 1 serves only as a diagnostic tool in DC and narrow band AC modes because modulation of the probe signal prevents a clear view of the field response. |
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| Voltage Output 2 |
The second voltage output provides a voltage proportional to measured field with the benefits of some signal processing. The output is produced by the DSP through a fast D/A converter. |
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| The output signal is updated at 40 kHz, giving good response for low to mid frequency fields. Signal quality degrades at high frequency because of the sampling rate. This voltage can be corrected for probe offset and for the nominal sensitivity of the probe. |
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| Voltage Output 3 |
The third voltage output provides a voltage proportional to measured field with the most signal processing of the three outputs. All probe compensation available to the display readings, including temperature compensation, can be performed on this output. The output is produced by the micro-processor through a high-resolution, 16-bit, D/A converter updated at 30 readings per second. This output can also be used for field control. |
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| Computer Interface |
Two computer interfaces are included with the Model 475, serial RS-232C and parallel IEEE-488. Both allow setup of all instrument parameters and read-back of measured values. The reading rate over the interface is nominally 30 readings per second but ranges from 10 to 100 readings per second are available. LabVIEW™ drivers are provided to instrument users – consult Lake Shore for availability. |
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| Hall Probe Selection |
Listed below are the probes that you can choose from to include with your Model 475. Our experts can guide you through the probe selection process. Other standard probes are available at an additional cost. Lake Shore prides itself on making every attempt to satisfy customer requests for special probes. If you need a custom probe, contact Lake Shore for availability. |
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| Axial Probes |
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L (in) |
D (in) |
A (in) |
Active
area (in) |
Stem material |
Frequency range |
Usable full scale ranges |
Corrected accuracy (% rdg) |
Operating temp range
(°C) |
Temp coefficient (max) zero |
Temp coefficient (max) calibration |
Contains temp sensor |
| HMNA-1904-VR |
4 ±0.125 |
0.187 dia
±0.005 |
0.005
±0.003 |
0.030 dia
(approx) |
Fiberglass epoxy |
DC to
20 kHz |
HSE
3.5 G,
35 G,
350 G,
3.5 kG,
35 kG |
±0.20% to
30 kG and ±0.25% 30 to 35 kG |
0 °C to
+75 °C
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±0.09 G/°C |
±0.015 %/°C |
Yes |
| HMNA-2502-VR |
2 ±0.063 |
0.25 dia
±0.006 |
0.015
±0.005 |
Aluminum |
DC to
10 kHz |
| HMNA-1904-VF |
4 ±0.125 |
0.187 dia
±0.005 |
0.005
±0.003 |
Fiberglass epoxy |
DC to
800 Hz |
HST-4
35 G,
350 G,
3.5 kG,
35 kG |
±0.10% to
30 kG and ±0.15% 30 to 35 kG |
±0.13 G/°C |
-0.005 %/°C |
| HMNA-2502-VF |
2 ±0.063 |
0.25 dia
±0.006 |
0.015
±0.005 |
Aluminum |
DC to
400 Hz |
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| Transverse Probes |
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L
(in) |
T
(in) |
W
(in) |
A
(in) |
Active
area
(in) |
Stem material |
Frequency
range |
Usable
full scale ranges |
Corrected accuracy (% rdg) |
Operating temp range
|
Temp coefficient (max) zero |
Temp coefficient (max) calibration |
Contains temp sensor |
| HMMT-6J04-VR |
4
±0.125 |
0.061
max |
0.180
±0.005 |
0.150
±0.050
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0.040
dia
(approx) |
Aluminum |
DC to
800 Hz |
HSE
3.5 G,
35 G,
350 G,
3.5 kG,
35 kG |
±0.20% to
30 kG; ±0.25% 30 to 35 kG |
0 °C to
+75 °C
|
±0.09 G/°C |
±0.015
%/°C |
Yes |
| HMNT-4E04-VR |
4
±0.125 |
0.045
max |
0.150
±0.005 |
Fiberglass epoxy |
DC to
20 kHz |
| HMMT-6J04-VF |
4
±0.125 |
0.061
max |
0.180
±0.005 |
Aluminum |
DC to
400 Hz |
HST-4
35 G,
350 G,
3.5 kG,
35 kG |
±0.10% to
30 kG; ±0.15% 30 to 35 kG |
±0.13 G/°C |
-0.005
%/°C |
| HMNT-4E04-VF |
4
±0.125 |
0.045
max |
0.150
±0.005 |
Fiberglass epoxy |
DC to
800 Hz |
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| Flexible Transverse Probes |
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Active
area
(in) |
Stem material |
Frequency
range |
Usable
full scale ranges |
Corrected accuracy (% rdg) |
Operating temp range
(°C) |
Temp coefficient (max) zero |
Temp coefficient (max) calibration |
Contains temp sensor |
| HMFT-3E03-VR |
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0.040
dia
(approx) |
Flexible
plastic
tubing |
DC to
20 kHz |
HSE
3.5 G,
35 G,
350 G,
3.5 kG,
35 kG
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±0.20% to
30 kG; ±0.25% 30 to 35 kG
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0 °C to
+75 °C
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±0.09 G/°C
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±0.015 %/°C
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Yes |
| HMFT-3E03-VF |
DC to
800 kHz |
HST-4
35 G,
350 G,
3.5 kG,
35 kG |
±0.10% to
30 kG; 0.15% 30 to 35 kG |
±0.13 G/°C |
-0.005
%/°C |
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