Theory Of Operation
The probe is a passive attenuator. See Table 1. High input impedance,
accuracy, and stability characteristics are achieved with thick-film
resistors. When the probe is connected to a voltmeter with a 10 MΩ input
resistance the probe becomes an accurate 1000:1 divider. This divider
depends on a ground lead to complete the low side of the circuit path. The
connection must always be secure before you do the voltage
measurement. Otherwise, instrument damage or a shock hazard can
result.
Table 1. Schematic Diagram
Voltmeter Compatibility
Accuracy of the meter is not included in the accuracy of the probe and
must be added to the probe accuracy to determine system accuracy.
The probe is mechanically compatible with any ac or dc voltmeter or
multimeter that accepts a standard double banana connector (spaced
0.75" [19 mm]) with standard plugs (0.160" [4 mm]).
The probe is electrically compatible with any ac or dc voltmeter or
multimeter that has an input impedance of:
• 10 MΩ ±1 % for 80K-40
• 10 MΩ ±10 % for 80K-6
Voltmeters or multimeters with other input impedances require the use of
an external shunt or a correction factor to obtain an accurate
measurement. Higher impedance voltmeters or multimeters should be
equipped with a shunt, and lower impedance voltmeters or multimeters
should be assigned correction factors.
Probe
Resistor
RA RB
80K-40 999 MΩ 1.11 MΩ
80K-6 75 MΩ 75 kΩ
Probe Tip
(Dual Banana Plug)
Protective
Earth Lead
RA
RB
10 MΩ
(Voltmeter)
HI
LO
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