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1021 Technical Manual
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3.
Operation
3.1. Preliminaries
The 1021 is supplied complete with rechargeable batteries (housed in the instrument) and a
mains charger. Before operation, the batteries should be checked on the battery level
indicator. It is important to recheck the battery condition when the instrument is supplying
currents in excess of a few tens of mA, since the additional load may reduce the battery
voltage to below the minimum level.
3.2. Normal Operation
Using the specification together with the front panel controls makes the operation self-
explanatory. It is important to understand the voltage capability and the voltage limit
indicator of the instrument to ensure that requirements are within limits.
3.3. Measurement of Current
1. Select NULL on the front panel function switch.
2. Select NORM output.
3. Adjust SENS fully anti-clockwise (minimum sensitivity).
4. Select RANGE consistent with the current to be measured.
5. Connect the unknown current such that it flows into the + ve terminal.
6. Adjust the digit switch and sensitivity control for null balance on the LED indicator
(green centre LED).
7. When balance at the required sensitivity is reached, the value of the unknown current
equals the digit switch setting.
3.4. Voltage Compliance Adjustment - V O/P
The minimum voltage compliance of approximately 14v is obtained by turning the V O/P
control fully anti-clockwise. With full clockwise adjustment approximately 40v is obtained.
The voltage level is checked by measuring across the output terminals when the voltage
limit LED is illuminated.
It is recommended that the voltage level is set to the minimum required for the work in hand.
3.5. Overload Conditions
The instrument can withstand either a short or open circuit on the output terminals
indefinitely. Overload conditions can result if an attempt is made to drive current into the
instrument by applying a voltage to the output terminals. In most cases this will cause the
output fuse to blow but could still damage the output circuitry.
3.6. Battery Recharging
Under normal conditions the 1021 should be switched off during battery recharge. Full
recharge takes 10-16 hours. The battery charging rate is such that the battery cannot be
damaged by overcharging.
It is not recommended that the 1021 be operated during battery recharge although output
currents of a few milliamps at low compliance voltage can be obtained without discharging
the batteries. It should be noted however that additional electrical noise will appear on the
output due to the indirect mains power connection.