Voltage and Temperature Measurements 2-9
Perform the following steps to enable or disable line cycle synchronization:
1. Press SHIFT and then LSYNC to display the present state of line synchronization (OFF
or ON).
2. Use or key to display “ON” or “OFF.”
3. Press ENTER. The instrument returns to the normal display state.
NOTE Line cycle synchronization is not available for integration rates <1 PLC, regardless
of the LSYNC setting.
Pumpout current (low charge injection mode)
Pumpout current for Channel 1 is very low (0.5µA peak-to-peak) and therefore, does not
adversely affect instrument performance. Channel 2 can make the same claim as long as Channel
2 LO is connected to Channel 1 LO. This pumpout current is due to internal switch transitions,
and occurs between A/D conversions. Settling for the transition occurs on the next A/D
conversion. Whenever the impedance between Channel 2 LO and Channel 1 LO is >100kΩ,
pumpout current could be high enough to corrupt measurements below 1V. Above 1V
measurements, pumpout current is not significant.
Low Charge Injection Mode — If you must use Channel 2 for measurements below 1V and
the impedance between Channel 2 LO and Channel 1 LO is >100kΩ, you can enable the Low
Charge Injection Mode to reduce the pumpout current. However, this mode increases
measurement noise by up to 8 times.
The Low Charge Injection Mode can be enabled or disabled from the GPIB or RS-232
interface. The command to control low charge injection is listed in Table 2-2. Low charge
injection cannot be enabled from the front panel. However, it can be disabled from the front
panel by restoring factory default conditions.
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