current will sometimes prevent a ‘Contact Limit’ error – this is in situations where
the sample has become damaged due to excessive current.
Press the ‘On/Off’ button to switch the HM21 off. Note that it can take up to 5
seconds for the unit to switch off – the button only needs pressing once!
This has now summarized the functions of the HM21 and you are ready to make
some measurements!
General Information
The current is changeable in 6 steps - 100nA, 1uA, 10uA, 100uA, 1mA, 10mA.
The compliance voltage is above 8.5V but slightly reduces to 7.5V at 10mA,
however 10mA would usually only be used with more conductive samples where
the compliance voltage is not so critical.
Overall accuracy is better than 0.5% where the DVM receives greater than 1mV.
For the mid ranges the accuracy is better than 0.3%
The DVM has two ranges - high sensitivity up to 150mV and low range up to
1.25V.
The unit is push button operated.
The current is increased with the 'INC' button and decreased with the 'DEC' button.
Forward and reverse current can be selected using the ‘FWD’ and ‘REV’ button.
When the battery mode is used the unit returns to standby automatically to save
power and turns off altogether after some period of inactivity.
The automatic time to return to standby is 70 seconds with low current and with the
3 highest currents 40 seconds. This is because the lower current ranges are used
with higher impedance which can take longer to settle, and the higher currents
drain the power faster.
The unit can be zeroed to remove any offset by pressing the Standby button when
the unit is already in Standby.
