Operation Manual

14 GMC-I Messtechnik GmbH
5.1 Insulation Measurement with Adjustable Test Voltage
A DC test voltage within a range of 50 to 1000 V can be selected with the
U
VAR
function for measurements at sensitive components and in
systems equipped with voltage limiting components.
Ð Select the U
VAR
function from the U
ISO
menu with the or the
key and acknowledge with the U
VAR
key.
Ð In order to enter the desired value:
Display the desired numerals, and if required the decimal point, with
the help of the and keys. Select the desired numerals with
the appropriate softkeys. Each time an entry is made, the cursor
moves one place to the right. After a maximum of three numerals
have been entered, exit the data entry window by pressing the 
softkey. If the selected voltage is not within the valid range, the cursor
jumps back to the entry position for the first digit.
After the value has been completely entered and acknowledged with
the START key, U
VAR
is displayed between R
ISO
and U
ISO
.
Ð The remainder of the measurement procedure is identical to the test
sequence used for predefined nominal voltages.
5.2 Measurement with Rising Test Current
The “U ” function can be used for the detection of weak points in
insulation, as well as for the determination of response voltage at voltage
limiting devices.
Ð Select the U function from the U
ISO
menu with the or the
key and acknowledge with the U
key.
As long as the START key is depressed, test voltage is continuously
increased. Insulation measurement begins:
• As soon as maximum voltage is reached (= variable test voltage, see
chapter 5.1) or
• As soon as the START key is released
(when the desired voltage appears at the display) or
• As soon as a measurable test current is detected (e.g. after a
discharge voltage sparkover).
Test voltage, any response or discharge voltages values and insulation
resistance are all displayed.
5.3 Setting the Limit Value
A limit value for insulation resistance can be selected with the LIMIT key. If
measured values are detected below the limit value, the red LIMIT LED
lights up.
START
START