Selectable Impedance Adapter

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The Selectable High Impedance Adapter is used to increase the effective input impedance of a “standard” voltmeter (having an input impedance of 10 MΩ or less), to selectable impedance values in the range, 20 MΩ to 200 MΩ. At the same time, the Adapter effectively filters AC noise. The provision of high input impedance combined with effective AC filtering, results in cleaner, more accurate DC voltage readings from your voltmeter, even when dealing with a high source resistance, such as would be the case when taking structure-to-soil potential readings with respect to a reference electrode, in high soil resistivity situations, for example.

The Adapter is supplied with two banana plug cables to connect the unit to a voltmeter.


  • Improves accuracy of pipe-to-soil readings
  • Compensates for high resistance contacts between soil and electrode
  • Adapts with any voltmeter
  • Switch selectable input impedance of 20 MΩ., 50 MΩ., 100 MΩ., 200 MΩ. or 1 GΩ/Open
  • Superior filtering of AC noise
  • Watertight enclosure
  • Small and convenient

Frequency Response
Frequency Attenuation Counts of Error
50 Hz -74.3 dB 1 in 5,210
60 Hz -85.6 dB 1 in 19,149

AC Rejection @ 50 Hz
Rejection Counts of Ripple Settling Time
6.36 Vrms 1 (± 1.5 mV) <200 ms
11.3 Vrms 2 (± 2.5 mV) <200 ms
17.7 Vrms 3 (± 3.5 mV) <200 ms

AC Rejection @ 60 Hz
Rejection Counts of Ripple Settling Time
19.1 Vrms 1 (± 1.5 mV) <200 ms
33.2 Vrms 2 (± 2.5 mV) <200 ms

Maximum AC noise before distortion occurs
Frequency AC noise
50 Hz 25.5 Vrms
60 Hz 34.0 Vrms

DC Response and Accuracy:
It takes the High Impedance Adapter less than 200ms to reach an output voltage of 2VDC +1mV with a 2VDC input.
Maximum operational DC input: +4V.

Input Impedance: Switch selectable (20, 50, 100, 200MO, 1GO).

Rejection is defined as the 60 Hz (50 Hz) RMS voltage required to cause the corresponding counts of ripple.
Settling Time is defined as the time for the output to be within the corresponding counts of ripple for each rejection.
Counts of Ripple refers to the amount of amplitude variation due to AC noise.

Selectable Bypass Polarity Switch:
1) In the ON position, the HIB will work in normal working capabilities.
2) In the OFF position, The HIB is completely turned off.
3) In the BYPASS position the HIB is being bypassed thru that is higher than 4V. Switch capacity is at 5A.

Battery:  9V alkaline or 9V lithium recommended.

Battery Life:
•Alkaline - greater than 60 hours of continuous operation (worst case).
•Lithium - greater than 210 hours of continuous operation (worst case).

Minimum battery voltage: 8.0 Volts

Operating temperature: -40oF to 185oF (-40oC to +85oC).

Overall: 3-1 /4" x 3-9/16" x 3" (8.3 x 9.0 x 7.6 cm)
Box: 3-1/4"x 3-3/16 x 2-3/16" box (8.3 x 8.1 x 5.6 cm)
Weight: 9.3 oz. (264 g)