DEKRA Process Safety

JCI 140 - Field Mill Static Monitor

Including the JCI 140F, JCI 140 X and JCI 140XF


  • Indicates surface voltage
  • Resolution to 1V & full scale 20kV (standard version, used as per manufacturer’s instructions)
  • Extended range available for higher voltages
  • Fast version available for high frequency AC fields (-3dB at 400Hz)
  • Field mill technology avoids the zeroing required for Induction Monitors.

General Description

The JCI 140 Static Monitor is a compact, easy to use instrument for direct non-contact measurement of surface voltage. It is available in 3 options: F – Fast Response, X – Extended Range & XF - Fast Response Extended Range. From a distance of 100 mm the 3½ digit liquid crystal display indicates surface voltage to an accuracy of 1 Volt. This makes it particularly easy to find even low levels of static charge and to make measurements with confidence.

As a field mill instrument there is no need to switch-on in a static free environment, no need for measurements to be made within a limited time and no need to worry about the influence of air ionisation – which are all concerns with simple ‘induction probe‘ type instruments. The novel mode of operation of the JCI 140, with no earthing of the rotor (the instrument must still be earthed), provides quiet, stable operation with fast response and long operational life.

The JCI 148 and JCI 146 are compatible modular voltmeter adapters for use with the JCI 140. Both instruments allow direct measurement of voltages on live conductors using a probe. The JCI 140, when used with the JCI 148, can measure voltages up to 20kV dc and the JCI 146 can measure voltages up to 60kV dc. The very high input resistance of these systems eliminates the loading effects suffered by many high voltage voltmeters and high voltage adapters for multimeters. The JCI 147 is a compatible modular Faraday Pail adaptor for use with the JCI 140. It allows direct measurement of charge (in nano Coulombs) on items placed in the Faraday Pail.

field mill static monitor


  • Ranges: 2kV & 20kV full scale
  • 1V and 10V resolution at 100mm
  • (20kV & up to 50kV for JCI 140X / XF, with precautions as per the manufacturer‘s instructions)
  • Response: -3dB at ~120Hz for standard JCI 140
  • -3dB at ~400Hz for JCI140F
  • Zero Stability: Within ±10V on 2kV range
  • Accuracy: Within ±2% FSD
  • Linearity: Within ±1% FSD
  • Display: 3½ digit LCD indicating surface voltage in kilovolts at 100mm with polarity and ‘LO BATT‘ indication
  • Audio alarm: Pulsing audio output when reading above user set alarm level
  • Signal outputs: Via 8 pin miniature DIN socket
  • Power Supply: PP3 Battery or JCI142 external mains adapter
  • Dimensions: 34x66x150mm overall. Weight: 320g.

Accessories & Services

  • JCI 143 Analogue Output Cable
  • JCI 142 External Mains Adapter
  • JCI 169 Permanent Mounting Feet
  • Digial USB Oscilloscope & Data Logger
  • Calibration to BS7506: Part 2:1996
  • JCI 125 Zero Check Chamber

Compatible Modular Instruments