Operating Instructions; Introduction; Measuring Current - Fluke A40B Instruction Manual

A40B
Instruction Manual

Operating Instructions

Introduction

This section of the manual describes how to measure both AC and DC current using any
one of the Current Shunts. The procedures are based on the assumption that the user is
familiar with the Operating Information and Specifications presented earlier in this
manual.

Measuring Current

Use the following procedure to measure current using one of the Current Shunts:
1. Analyze the circuit being tested and determine the following:
2. Select a Current Shunt capable of safely handling the estimated current.
3. If using the 1 mA Current Shunt, switch it to On and verify that the battery low (red)
4. Remove power from the circuit under test and connect the input of the Current Shunt
5. Connect an appropriate voltage measuring device to the output of the Current Shunt,
6. Apply power to the circuit and measure the resulting output voltage. This output
7. Use the voltage measurement and the Operating Information in the previous section
16
a. The approximate value of the current that flows in the circuit.
b. The frequency of the current to be measured (DC to 100 kHz).
indicator is off. If the 1 mA Current Shunt has been charging, disconnect the charger.
The charging process creates heat in the battery so for the best accuracy allow the
shunt temperature to stabilize for 100 minutes after charging completes.
in series with the circuit.
and select the correct range. The output voltage of the Current Shunt is proportional
to the input current; 0.8 V for nominal rated current.
It is generally appropriate to set the measuring device to remote guard and connect its
guard terminal to the guard on the Current Shunt. Refer to the measuring device
documentation.
voltage is directly proportional to the current flowing in the circuit.
of this manual to accurately determine the current level.
Determine the current using the following formula:
Where: AC-DC calibrated and Loading error are expressed in ppm.
⎛ ⎞
⎛
V
⎜ ⎜ ⎟ ⎟
= ×
⎜
I
R
⎝
⎝ ⎠
calibrated
⎞
AC - DC
+ ×
⎟
calibrated
1
1,000,000
⎠
⎛ ⎞
Loading error
−
⎜ ⎟
1
1,000,000
⎝ ⎠