Products > Electrostatic Voltmeters > Non-Contacting

Model 368A High-Speed Electrostatic Voltmeter

The Trek Model 368A High-Speed Electrostatic Voltmeter provides precision noncontacting measurement of the surface voltages associated with electrostatic imaging processes as employed by the electrophotographic reproduction and laser printing industries. Highly accurate electrostatic voltage measurements are also associated with applications such as photoreceptor research and semiconductor processing. The Model 368A is used in research and development applications and to measure electrostatic potentials on objects or surfaces such as polymer, film, fabric, and paper.

The miniature sensor probes utilize a patented dual chopper design. This design provides high-speed, DC stable measurements with exceptional low noise and drift performance in wide temperature range conditions, under high humidity, and even in the presence of contaminating particulates. Sensor probe options include standard or high-temperature probes with either an end-viewing or side-viewing orientation.

The voltage of moving or stationary surfaces can be easily measured with high accuracy over a wide range of sensor probe to measured surface spacings. The noncontacting measurement ensures that no charge transfer will take place to modify or destroy the actual data.

A user selectable dual range precision voltage monitor provides a low-voltage replica of the measured electrostatic voltage for external monitoring purposes or for use as a feedback signal in a closed loop control system.

Rack mount options are available to permit up to four independent measurement channels in a standard full rack or for compact bench top operation.

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All specifications are with a probe to surface separations of 2 mm, ±1mm.

Measurement Range
0 to ±2 kV DC or peak AC.

Measurement Accuracy
Voltage Monitor Output

Better than ±0.1% of full scale.
Voltage Display
Better than ±1% of full scale, referred to the voltage monitor.
Note: The measurement accuracy degrades to ±1.5% of full scale in the presence of line transients per IEC 801-4.

Speed of Response (10% to 90%)
Less than 200 µs for a 1 kV step change.

Drift with Time

Less than 100 ppm/hour, noncumulative.
Drift with Temperature
Less than 200 ppm/°C.


Power ON/OFF
Two position toggle switch.

Zero Control
A 10-turn control to null offsets that may be present at the voltage monitor output when the Model 368A is measuring zero volts.

Voltage Monitor Output
A BNC providing a low-voltage representation of the measured voltage.
1/ 200th or 1/1000th of the measured voltage (switch selectable). Calibration potentiometers for both ratios are accessible from the front panel.
Output Noise
Less than 25 mV rms (measured using the true rms feature of the Hewlett Packard Model 34401A digital multimeter).
Output Impedance
Less than 0.1 Ω.

Voltage Display
3-1/2-digit LED display.
0 to ±1999 V.
1 V.
Zero Offset
Better than or equal to ±1 count, referred to the voltage monitor.
Sampling Rate
2.5 readings per second.

Model Ordering Information

Item /Part Number (Add the suffix L for 90 to 127 V AC operation and the suffix H for 180 to 250 V AC operation.)

Stand-Alone Instrument 

Half-Rack, One Channel 

Half-Rack, Two Channels

Full-Rack, One Channel

Full-Rack, Two Channels

Full-Rack, Three Channels 

Full-Rack, Four Channels 


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

Standard Resolution Probes
Model 3800E-2  end-viewing.
Model 3800S-2  side-viewing

High Temperature (to 60 °C)
Model 3870ET-2  end-viewing.
Model 3870ST-2  side-viewing.

Probe Ordering Information

Part Number. 

Model 3800E-2 (end viewing) 

Model 3800S-2 (side viewing) 

High-Temperature (up to 60°C)
Model 3870ET-2 (end viewing) 
Model 3870ST-2 (side viewing) 

Model 3800EC-2 Probe Extension Cable 



Stand-Alone Instrument

133 mm H x 113 mm W x 341 mm D
(5.3" H x 4.5" W x 13.5" D).
Half Rack (holds up to two channels)
133 mm H x 271 mm W x 353 mm D
(5.3" H x 10.7" W x 13.9" D).
Full Rack (holds up to four channels)
133 mm H x 483 mm W x 353 mm D
(5.3" H x 19" W x 13.9" D).

Stand-Alone Instrument

2 kg (4.4 lb).
Half Rack
1.5 kg (3.3 lb), add 1.5 kg (3.3 lb) per channel.
Full Rack
2.5 kg (5.5 lb), add 1.5 kg (3.3 lb) per channel.

Voltage Monitor Connector
BNC coaxial connector.

Ground Receptacle
Banana jack.

AC Line Cord Receptacle
Standard IEC320 three-prong AC line connector with an integral fuse holder.


Power Requirements
Line Voltage
Factory set for one of two ranges: 90 to 127 V AC or 180 to 250 V AC, at 50/60 Hz (specify when ordering).

Power Consumption
35 VA, maximum.

Operating Conditions

0°C to 35°C.
Relative Humidity
To 85%, noncondensing.
To 2000 meters.

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


Accessories Supplied

  • Operator’s manual and line cord for each channel.


  • Full-Rack Mounting Kit

    1/2-Rack Mounting Kit


TREK, INC. certifies that each Model 368A 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.
Low Voltage Safety Compliance
Overvoltage Category
CAT II: Local-level mains, appliances, portable equipment.
Pollution Category
Degree 1: Operate in environments where no pollution or only dry nonconductive pollution occurs.

All specifications are subject to change.


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