Measurement Computing DBK Part 2 - Manual (Page 56)

DBK43A & DBK43B, pg. 36 899892 DBK Option Cards and Modules
“Mode = Bridge,” Reference Route
3. Turn off all the channels in the system except for those DBK43A [or DBK43B] channels that
are to be adjusted.
4. Click the Download button to send the current configuration to the LogBook.
5. Select Indicators \ Enable Input Reading Column from the menu bar to display the offset
values for each channel.
6. For the associated channel, set the offset voltage to 0.0V for each transducer by adjusting the
trimpot labeled OFFSET.
Note: If you are unable to nullify the quiescent offset of the bridge, your Input Amplifier
gain may be too high. Information regarding gain redistribution can be found in the
section entitled, Determining the Gain of Each Amplification Stage.
7. Select Indicators \ Disable Input Reading Column from the menu bar.
2-Point Calibration
This 2-point calibration method makes use of trimpot adjustments. It should not be
confused with the LogView software 2-Point Calibration (discussed in the LogView
chapter in the LogBook User’s Manual).
In the 2-Point calibration method, the user places two known loads on the gage, one at a time, then adjust
the trimpots until the expected value is reached. Typically, the first of loads is “no load.” In the case of a
weight scale, the scale would first be unloaded to adjust the offset, then a known load (near maximum
expected) would be applied to adjust the gain.
Shunt calibration (discussed immediately after this 2-Point Calibration section) is the same as the 2-Point
method, except the second load is applied in a simulated fashion by shunting 1 leg of the bridge with a
shunt resistor. Shunt calibration is preferred in cases where applying a real load (near the maximum
expected) is not practical.
Initialize the System
1. DBK43A users: Verify that the unit’s physical switch is in the NORM position.
DBK43B users: Verify that the unit’s physical CAL1 and CAL2 switches are both in the
RUN position.
2. Download a single setup and continuously display data in LogView. The continuous display
can remain throughout the procedure since the calibration multiplexers do not need reset
between steps.
3. In the Param1 column (see page 29 for location), select all of the DBK43A [or DBK43B]
channels that are to be adjusted.