Null Indicator; Checking The Null Indicator - Sartorius Basic plus Service Manual

Important note:
Procedure:

Null Indicator

Checking the Null Indicator

Never change the position of the null indicator! Even when the lever is
removed, the null indicator does not require adjustment.
- Open the balance (see page 27).
- Connect the digital voltmeter between pin 7 of the IC 101 on the analog
PCB (204b) and the ground (⊥).
- Set the measuring range of the digital voltmeter to 20 V DC.
- Switch the balance back on.
- The lever (E) must be able to move freely between the upper and lower
stops (F, G).
- Carefully move the lever (E) against the lower and upper stops (F, G).
- The following voltages should be read at the null indicator output port:
approx. - 2.5 V when the level stabilizes, and approx. ± 1 V (relative to
the voltage at the stabilization point) when the lever reaches the stops.
Example: - 1.63 V ... - 2.47 V ... - 3.58 V
If the difference in voltage at the upper and lower stops is not symmetric, or if
the lever pulls toward the upper or lower stop when the balance is switched
on, this might indicate a mechanical or electrical error.
- If the voltage readings at the stabilization point and at the upper and lower
stops are correct, we recommend checking (and, if necessary, adjusting)
the preload (see page 25) before you close the balance
(see page 27).
SARTORIUS Basic plus
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