The Trek Model 325 Electrostatic Voltmeter is a versatile instrument used for performing noncontacting electrostatic voltage measurements in applications which include contact potential (surface work function) determination, materials evaluation and electret studies. The Model 325 was specifically designed for high sensitivity applications to allow highly accurate, low noise, noncontacting measurement of electrostatic voltages of 0 to ±40 V over a wide range of probe-to-surface distances.
Special features of the Model 325 allow tuning the performance of the unit to compensate for specific test conditions. A calibrated Null Voltage supply of ±10 volts nulls measured surface contact potential when measuring voltages on associated metallic test surfaces. A response Speed Control adjusts the AC response of the Model 325. A Drift/Spacing Null Adjustment minimizes the variation in monitored voltage values as the probe to test surface spacing changes.
A dual range front panel 3½ digit LED display resolves ±10 mV. The measured voltage can also be monitored through a precision 1:1 voltage monitor output and/or a 10:1 voltage monitor output.
Trek’s patented low impedance probe sensor assures measurement accuracy which is essentially independent of probe-to-test-surface spacing while eliminating the external environmental effects of high humidity and contamination, such as airborne dust, toner, ions and chemicals, on measurement accuracy.
The Model 325 can be operated as a bench top unit or, with optional hardware, in a half 9½-inch or standard 19-inch rack.
All specifications are with a Model PD1216P probe with a probe-to-surface separation of 0.4 mm.
Speed of Response (10% to 90%)
During operation, the metallic surfaces of the probe are driven to voltage levels equal to the measured surface voltage value. A probe holding fixture, should be of a insulating material with dissipative properties (107 to 1011 Ω/square) to prevent shorting of the probe to ground. Phenolic or other dissipative type material is recommended to avoid any fixture material charge retention.
Recommended Probe-to-Surface Separation
Model PD1216P Sensor Probe
Probe Cable Length
Null Voltage Source
Voltage Monitor Output (1:1)
Voltage Monitor Output (10:1)
Response Speed Control
Drift/Spacing Null Adjustment
Voltage Monitor Connectors
AC Line Cord Receptacle
TREK, INC. certifies that each Model 325 is tested and calibrated to specifications using measurement equipment traceable to the National Institute of Standards and Technology or traceable to consensus standards.
All specifications are subject to change.