User manual

Calibrating DBK16 and DBK43A for LogBooks
Reference Note
:
This section covers calibrating a DBK16 that is being used in a LogBook application.
Daq users: Refer to Calibrating DBK16 and DBK43A for Daq Devices, which begins on page 9.
Overview …… 15
Calibration Methods …… 16
Procedures Common to All Calibration Steps (Required) …… 17
Nameplate Calibration and Manual Calibration …… 20
Channel Calibration Procedure …… 23
2-Point Calibration …… 26
Shunt Calibration …… 28
Creating a Units Conversion Transfer Function …… 30
Periodic Calibration Without Trimpots …… 31
Overview
Calibrating a strain gage channel includes:
•
One-time adjusting of the bridge excitation.
•
One-time tuning of the electronic gains and offset via trimpots to maximize performance and dynamic
range.
•
Applying a transfer function to the voltage output to convert it to engineering units, e.g., pounds,
kilograms.
•
Executing a software scale and offset adjustment periodically to maintain accuracy.
Example of a Unit Conversion from Voltage to Pounds
The trimpots provide course tuning so large quiescent offsets can be nulled and the bridge signal can be
amplified to match the A/D input range. Once these adjustments are made, the operator can periodically
fine-tune the calibration via software using LogView’s 2-Point calibration feature. LogView’s scale and
offset features provide a simple means to apply a transfer function that converts the voltage to user units,
for example, pounds, as in the above block diagram.
Bridge circuit transducers are used for many different applications, and the strain gage signal conditioning
modules are flexible enough to support most of them. Each channel circuit has an excitation regulator, a
high gain (x100 to x1250) input amplifier with offset adjustment, a low-pass filter, a scaling (x1 to x10)
amplifier, and a calibration multiplexer.
DBK Option Cards and Module 879895 DBK16, pg. 15