Model 370 DC Stable Electrostatic Voltmeter

The Trek Model 370 is a precision electrostatic voltmeter with the unique capability of making noncontacting surface voltage measurements in the range of 0 to ±3 kV DC or peak AC.

The 370 employs an electrostatic field-nulling technique which achieves high DC stability and high measurement accuracy even if the probe to measured surface spacing changes. This permits measurements of either stationary or moving surfaces without the need to establish fixed spacing to maintain accuracy.

An automatic gain feature of the Model 370 eliminates the need for manual adjustment when changing probes or when changing the probe to measured surface separation.

The Model 370 also features one-step, push-button zeroing. When the ZERO button on the front panel is pressed, the Model 370 automatically adjusts the output to zero volts when the probe is coupled to a known zero volt surface.

A precision voltage monitor provides a low-voltage representation of the measured electrostatic voltage for external monitoring purposes, or for use as a feedback signal in a closed-loop system.

An optional data acquisition module is available, featuring an IEEE-488 compatible interface, 14-bit resolution, 12-bit accuracy, and a programmable sampling period from 10 µs to 30 minutes.

The Model 370 can be operated on a bench top or, with optional hardware, in a standard 19-inch rack.

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PERFORMANCE

• All specifications are with a 3800E-2 probe with a probe-to-surface separation of 2 mm unless otherwise noted.

  Measurement Range
  0 to ±3 kV DC or peak AC

  Measurement Accuracy
  Voltage Monitor Output
  Better than ±0.05% of full scale.
  Voltage Display
  Better than ±0.1% of full scale + 1 count, referred to the voltage monitor.

  Speed of Response (10%to 90%)
  Less than 50 µs for a 1 kV step.

  Stability
  Drift with Time
  Less than 150 ppm/hour, noncumulative.
  Drift with Temperature
  Less than 100 ppm/°C.

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PRODUCT FEATURES

• Zero Control
  A momentary push-button switch to produce zero volts output when the probe is coupled to a known zero volt surface.

  Automatic Gain
  The Model 370 automatically optimizes the AC response when changing the type of probe being used or when changing the probe-to-surface separation.

  Digital Enable
  An open collector, TTL compatible input to enable or disable the measurement. A TTL high (or open) will disable the measurement. A TTL low will enable the measurement.

  Voltage Monitor Output
  A buffered output providing a low-voltage replica of the measured voltage. 1/200, 1/300, 1/600, 1/1000 options available. (Offset Voltage and Output Noise specifications vary based on output scale factor.)
  Scale 
  1/100th of the measured voltage.
  Offset Voltage (at 1/100th scale)
  Less than 10 mV.
  Output Noise (at 1/100th scale)
  Less than 20 mV rms (measured using the true rms feature of the Hewlett Packard Model 34401A digital multimeter).
  Output Impedance
  Less than 0.1 ohm.
  Output Current Limit
  ±10 mA.

  Voltage Display
  4-character, 7-segment LED display.
  Range
  0 to ±3000 V.
  Resolution
  1 V.
  Zero Offset
  ±1 count, referred to the voltage monitor.
  Sampling Rate
  2.5 readings per second.

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Data Acquisition Module (Optional)

Provides data output using an IEEE-488 compatible interface.
Resolution
14 bit.
Accuracy
12 bit.
Sampling Period
Programmable from 10 µs to 30 minutes.
Storage
32 Kbytes (16 Kbytes of data words).
Acquisition Start Signal
External trigger or IEEE-488 Talk Enable or Group Trigger command.
Successive Data Acquisition
Internal timer or external trigger.
Interface Functions
SH1, AH1, T6, L4, SR1, RL1, PP0, DC1, DT0, C0, E2.
Address
Switch selectable between 0 and 30.

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ACCESSORIES

• Accessories Supplied
  • Operator’s manual, an IEC line cord for 90 to 127 V AC voltage source, or an unterminated power cord for a 180 to 250 AC line with the international color code as follows: brown-line, blue-neutral, and green/yellow-ground.

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GENERAL

• Power Requirements
  Line Voltage
  Factory set for one of two ranges: 90 to 127 V AC or 180 to 250 V AC, at 50 to 60 Hz.

  Power Consumption
  100 VA, maximum.

  Operating Conditions
  Temperature
  0°C to 40°C.
  Relative Humidity
  To 85%, noncondensing.
  Altitude
  To 2000 meters.

  Probe-to-Surface Separation (recommended)
  2 mm ±1 mm.

  Dimensions
  108 mm H x 223 mm W x 430 mm D
  (4.25" H x 8.75" W x 17" D).

  Weight
  5 kg (11 lb).

  Voltage Monitor Connector
  BNC coaxial connector.

  Digital Enable
  BNC coaxial connector.

  Ground Receptacle
  Binding post.

  AC Line Cord Receptacle
  Standard IEC three-prong line cord receptacle with an integral fuse holder.

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CERTIFICATION

TREK, INC. certifies that each Model 370 is tested and calibrated to specifications using measurement equipment traceable to the National Institute of Standards and Technology or traceable to consensus standards.  A Certificate of Calibration accompanies each instrument when it is shipped from the factory.

Copyright © 2004 TREK, INC.  All specifications are subject to change.

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