Products > Electrostatic Voltmeters > Non-Contacting

Model 344 Electrostatic Voltmeter

The Trek Model 344 is a precision electrostatic voltmeter for making noncontacting surface voltage measurements in the range of 0 to ±2 kV DC or peak AC.  Industrial applications include radiation effect  studies, R&D of the electrophotographic processes, and charge accumulation monitoring of the semiconductor production process.

The Model 344 employs a field-nulling technique for noncontacting voltage measurement that achieves DC stability and high accuracy even if the probe-to-surface spacing changes. This permits measurements of either stationary or moving surfaces without the need to establish fixed spacing to maintain accuracy.

The Model 344 patented probe design eliminates the need for close tolerance components. This significantly improves noise and drift performance, both in the presence of contaminating particulates and under conditions of high humidity and wide temperature ranges.

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

An optional Digital Enable feature can provide a connection for a remote device to turn on and off the high voltage of the instrument. This makes the Model 344 suitable for automated or computer-controlled systems.

The Model 344 can be operated on a bench top or, with optional hardware, in a standard 19-inch rack. The rack adapter allows two units to be mounted together.

Show/Hide Product Technical Information


All specifications are with a 6000B-8 probe at a probe-to-surface separation of 2 mm.

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

Voltage Monitor Output
Better than ±0.05% of full scale.
Voltage Display
Better than ±0.1% of full scale referred to the voltage monitor.

Speed of Response (10% to 90%)
Less than 3 ms for a 1 kV step.

Drift with Time

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


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

Standard Resolution Probes
Model 6000B-7C  end-viewing, round body.
Model 6000B-8  side-viewing, round body.
Model 6000B-15C  end-viewing, square body.
Model 6000B-16  side-viewing, square body.

High Resolution
Model 6000B-5C  end-viewing, round body.
Model 6000B-6  side-viewing, round body.
Model 6000B-13C  end-viewing, square body.
Model 6000B-14   side-viewing, square body.

Model 555P-4  end-viewing, square body.
Model 555P-1  side-viewing, square body.

High Temperature (up to 100 °C)
Model 6300-7  end-viewing, square body.
Model 6300-8  side-viewing, square body.

Probe Connector Locations
Model 344
Front panel.
Model 344-1
Back panel.
Model 344-6
Front panel.
Model 344-9
Front panel.



Zero Control
A ten-turn control to null offsets that may be present at the voltage monitor output when the Model 344 is measuring zero volts.

Response Control
A ten position push-button switch that adjusts the gain of the Model 344 to optimize the AC response. The response control is normally adjusted when changing the type of probe being used or when changing the probe-to-surface separation.

Voltage Monitor Output
A buffered output providing a replica of the measured voltage.
Model 344
1/100th of the measured voltage.

Output Noise
Less than 2 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
Less than ±1 count.

Digital Enable (optional)
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.




Accessories Supplied

  • Operator’s manual and line cord.


  • 344RA Full-Rack Mounting Kit
    (two instrument capacity)

    6003B Probe Line Driver (required when a very long probe extension cable is used)

    6004B-EC Probe Extension Cable (from 344 to line driver)

    6005B-EC Probe Extension Cable (from 344 to probe)


Line Supply
Factory set for one of three ranges: 100, 115, or 230 V AC, at 48 to 63 Hz
(specify when ordering).

Operating Conditions

0°C to 40°C.
Relative Humidity
To 90%, noncondensing.

64 mm H x 220 mm W x 270 mm D
(2.5" H x 8.7" W x 10.6"D).

2 kg (4.4 lb).

Voltage Monitor Connector
BNC coaxial connector.

Ground Receptacle
Banana jack.

AC Line Cord Receptacle
Standard three-prong line cord receptacle.

Power ON/OFF
A toggle switch


TREK, INC. certifies that each Model 344 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.

All specifications are subject to change.


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