Operation - Time Electronics 1018 Technical Manual

5. Operation

Page 7
Preparing for Use
After switching on the power and checking that the battery level is OK indicated by the 'low
batt' LED being fully lit. If it is dim or not lit you must recharge the batteries by plugging the
unit into the mains supply. It will take approximately 12 – 14 hours to fully recharge the
battery pack. However, the 1018 may used while it is connected to the mains supply,
irrespective of the battery state.
Basic operation
Before switching on it is wise to disconnect any load from the output terminals. Set the
output switch to 'off' before switching on, then select the required range and dial up the
required output value on the digit switch. The output terminals can then be connected and
the signal connected by operating the output switch.
Note – When the output switch is set to the 'off' position, there is a short circuit on the output
terminals.
Caution against minor electric shock must be exercised when using the 100V range. Also
take care not to overdrive any equipment connected to the unit (the max output current is
limited to about 10mA). Always check your wiring and connections carefully before switching
on.
Thermal emfs
When using the unit to provide a precision voltage of less than 1mV, care must be taken to
avoid Thermal emfs. These occur where temperature differences are present at the
junctions of dissimilar metals, e.g. A normal solder to copper junction has a thermal emf of
approximately 3uV/°C. Errors in the unit under stable temperature conditions are typically
less than 2uV. Always check the output from the unit with zero set. If very accurate low level
calibration is required a correction in the output setting must be made to compensate for the
thermal emfs.
Using the Deviation Control
Note : The digital deviation function operates only on the voltage and current outputs, not on
the resistance output.
To apply a percentage deviation to the output, select either positive or negative deviation
with the control switch and dial up the percentage deviation required on the digit switch.
Direct % error read-out when calibrating:
The output is set to the required nominal value. The Deviation function should then be used
to bring the reading on the unit being calibrated to the nominal value. The Deviation setting
is then the accuracy of the unit in % of the nominal. This method of calibrating is much faster
than using only the nominal value and will require mathematical calculation each time to
calculate the % error.