# Why use a multimeter with low input impedance?

#### Jim Hunter

Joined Jan 27, 2013
9
In looking for a digital multimeter, I came across the Fluke 113 on eBay. I found out it has low input impedance (according to the specs, 3 k$$\Omega$$). What I don't understand is: why would one want such a device? Doesn't it make it pretty useless as a voltmeter if the input impedance is low? (I thought the whole point was to have I high resistance in the voltmeter so that current through the voltmeter was low)

#### Jaguarjoe

Joined Apr 7, 2010
767
The 113 is a "utility" meter made for industrial or utility company electricians.

The low-Z input is useful for AC measurements on wiring that is closely bundled together, such as at the end of a long conduit run. Stray voltages will appear on otherwise open wires due to capacitive coupling with the live wires in the bundle.

#### Audioguru

Joined Dec 20, 2007
11,249
The Fluke 113 multimeter is made to be used for Utilities, not for electronic circuits.

#### BillB3857

Joined Feb 28, 2009
2,533
In some tests, loading is required to prevent phantom readings. The unit you are looking at provides some. The photo shown in your link shows an industrial electrician making a test on power equipment. Where I worked, we were required to use a Wiggi (solenoid type) testing unit for checking 440VAC fuses, etc. The electronic type DVMs were used for electronic work.

An interesting read is here.... http://en.wikipedia.org/wiki/Solenoid_voltmeter

#### #12

Joined Nov 30, 2010
18,210
Another good use is in checking small batteries like the CR2032 used for CMOS memory in computers. With a 10Meg meter, bad batteries look fairly good. Add a 1ma load (3k ohms) and the bad ones betray themselves by dropping to an obviously wrong voltage. I have to alligator a 3.3k resistor to my Fluke probes to test batteries or I'll get false readings.