Operator SafetyW, Theory Of Operation | Fluke 80K-40 specification

Operator SafetyW

Indicates the operator must refer to an explanation in this manual.

Indicates terminals at which lethal voltages may exist.

Warning

Circuit Loading

The 80K-40 represents a 1000 MΩ load to the circuit being measured, or 1 μA per 1 kV. Table 1 shows the circuit loading and input/output characteristics of the probe over its measurement range.

Table 1. 80K-40 Circuit Loading and Input/Output Characteristics

∙ To avoid damage or electric shock:

∙ Use within ratings and under dry (no

condensation) conditions.

∙ The 80K-40 user should be familiar with, and

exercise, all possible high voltage safety

practices.

∙ When making a measurement, never make body

contact with the probe tip or the red portion of the

probe. Always hold the probe by its black handle.

∙ Before making a measurement, make sure that

Input Voltage

10V

100V

1kV 10 kV 20 kV 30 kV 40 kV

Loading Current

10 nA

100nA

1μA

10μA

20μA

30μA

40μA

Output Voltage

10mV 100 mV

10V

20V

30V

40V

the tab side of the output connector is connected

to the voltmeter’s low input terminal.

∙ The clip lead must be attached to earth ground.

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 80K-40 is mechanically compatible with any ac or dc voltmeter or multimeter capable of accepting a standard spaced, 0.75" (19mm) double, banana plug, having standard, .160" (4mm) plugs.

The 80K-40 probe is electrically compatible with any ac or dc voltmeter or multimeter that has an input impedance of 10 MΩ

±1%. 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. Applicable formulas follow:

a.The following formula is used to determine the value of an external shunt resistor (meter impedance >10 MΩ):

Operation

Use the following procedure to operate the 80K-40:

1.Select and energize a compatible voltmeter.

2.Equip the voltmeter with a suitable shunt, if required.

3.Select an appropriate voltage range (1 volt reading per 1000 volt input. See Table 1).

4.Connect the probe’s output leads to the voltmeter input terminals.

5.Connect the probe’s clip lead to ground. See OPERATOR SAFETY.

6.Connect probe tip to circuit being measured and observe voltmeter reading. Apply correction factor to reading when necessary.

Theory Of Operation

The 80K-40 High Voltage probe, is designed to extend the voltage measurement range of an ac/dc voltmeter up to 40,000 volts. Electrically, the probe is a passive attenuator as shown in Figure 1. Its high input impedance (1000 MΩ), as well as its accuracy and stability characteristics are achieved through the use of special thick film resistors. When the probe is connected to

= Rm x 10

Rm − 10

a voltmeter with a 10 MΩ input resistance the probe becomes an accurate 1000:1 divider. Notice that the divider depends upon a

Where: Rs = Shunt resistance in MΩ

Rm = Voltmeter input impedance in MΩ (>10 MΩ) Example: If RM = 20 MΩ,

Rs = 20 x 10 = 200 = 2.0MΩ 20 − 10 10

b.Use the following formula to calculate a correction factor (meter impedance <10 MΩ):

ground lead to complete the low side of the circuit path. Therefore, this connection must always be secure before attempting a voltage measurement. Otherwise, instrument damage or a shock hazard will result.

80K-40	DC Voltmeter
Probe Tip
	HI
Replacement Resistor Kit	10MΩ

= 1.11 + Rm

1.11 x Rm

PN 939335	LO

Where: Cf=Correctionfactor (multiplier for meter reading)

Rm = Voltmeter input impedance in MΩ Example: If Rm = 1 MΩ,

Cf = 1.11 + 1 = 2.11 = 1.901 1.11 x 1 1.11

Therefore: A meter reading of 0.526 volts represents an

input of: 0.526 x 1.901 = 1 or 1 kV.

Ground

Lead

Fluke 80K-40 Operator SafetyW, Theory Of Operation, Circuit Loading, Voltmeter Compatibility

Models: 80K-40