Table 3-1. Controls, indicators, and connectors (cont.)

DC Low Frequency Thermal Measurments
Page Navigation
47

Table 3-1.

Controls, indicators, and connectors (cont.)

e. Various sources of error may be present when employing the ATS.

These

sources are detailed below so that the user may be familiar with them and allow for

them to obtain maximum accuracy.

(1) Loading effects.

The input impedance of the ATS, particularly on the

low voltage ranges, is relatively low (due to the current required for the

thermoelement heater and the shunt input capacity presented by the relay connected

range attenuator) and will have a loading effect when connected to the voltage

source under test. Voltage sources having a nonzero output impedance and/or poor

regulation characteristics will develop two different output levels; one while the

ATS is in the AC balancing state (loading the source) and a second when the ATS is

in the DC transfer state (voltage source removed from ATS input attenuator). The

output voltage of the ATS, as indicated on the readout instrument, will be the

voltage of the loaded source.

(2) Losses in interconnecting wiring.

Since the ATS has an output

impedance of approximately 200 ohms/volt, the voltage drop in the wiring

interconnecting the voltage source and the ATS may introduce a measurement error,

particularly when the low voltage ranges are employed.

It is recommended that

short heavy leads be employed when interconnecting the equipment.