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Display Instrument Impedance

This page applies to sensors shown at Sensors 5 Hz-1 MHz 

For best accuracy we recommend using display instrument with input impedance equivalent to or better than our calibration instrument, which is 10 Megaohms shunted by less than 30 pF. Below 30 kHz frequency we may use 1 Megaohms shunted by 100 pF. 

If your display instrument has 50 ohm input impedance, then we strongly recommend you use a high impedance adapter or high impedance probe with low capacitance for your display instrument.

Also at a sharp high resonant peak seen for some sensors (MC95R, MC95RW, MC90R, MC110R), the impedance you present to the sensor can affect the resonant frequency and the output voltage near resonance and at higher frequencies above resonance.

Coax Length: At frequencies above 30 kHz, the length of coax cable you use to connect the sensor to your display instrument can also significantly affect results. If the sensor has no built-in coax cable, then for calibration tests we used a 37-inch (0.94m) long coaxial cable which has 66 pF capacitance in shunt to the display instrument input.