USER’S MANUAL
36
Pre-setting a current value
If your test object’s load is consistently linear, the
Preset function provides a
method to set a current value while the output switch is in the OFF position.
When
Preset is active, the unit calculates the current that would result from
each position of the regulation knob at the ‘flagged’ current tap over the
connected impedance. This theoretical value is shown in Display #2 though
no current is actually being injected. This is possible by applying the formula
where |V| is the voltage that corresponds to the present position of the
variac at the current tap where impedance |Z| has been previously meas-
ured and stored (see Measurement Functions at the DESCRIPTION chapter).
This calculated current adjustment is useful when you need to test one relay
over multiple settings in the same current tap. Beware, though, that the ac-
curacy of this calculation is compromised when the connected load has a
substantial amount of reactive (inductive or capacitive) components.
If you want to regulate the current before activating the output, do the fol-
lowing:
1) Check that the output is switched off and the variac is at its mini-
mum (“0”) position.
2) Connect the load to the current output that best accommodates the
regulation range and flag it using the button.
3) Go to the |Z|tap function using the and but-
tons.
4) Without exiting the Func. mode, activate the unit’s output and regu-
late it to a minimum 10 percent of the intended test current’s upper
limit. For example, if you are going to test between 5 and 20 A, re-
gulate a little bit more than 2 A now.
5) Display #1 will be showing the measured impedance as you regu-
late the current. Press now to save it into memory and
switch the output off.
Enter/Print
Function
Tap
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