Internal Gain; Setting Internal Gain With Calibration Signal - KYOWA DPM-900 Series Instruction Manual

5-7 INTERNAL GAIN

Setting methods for the internal gain are the following 3 methods that use CAL, TEDS, or ACTL LOAD.
In general, CAL is used.
When the measuring target is the TEDS installed strain gage transducer, set the internal gain with the
TEDS for easy setting.
If you want to set the internal gain with the actual load or external calibrator, set the internal gain with the
ACTL LOAD.
Selection of the smallest internal gain (× 200) lets you cover up to ±50000 m/m measuring range.
However, with this internal gain, a maximum output is rated at as small as 20 mV or there against a strain
input of 100 m/m. This means poor precision of measuring.
By contrast, the largest internal gain (× 20000) causes saturation against a large strain input.
Accordingly, an appropriate internal gain should be selected so as to meet the amount of a strain to be
measured.
The larger the internal gain is selected, the larger an amplification degree becomes, resulting in large noise.
NOTE
The internal gain setting range of the DPM-900/950 series is × 200 to × 20000.
If you want to set the internal gain with the CAL either × 200 or × 20000, set the CAL and
VOLTAGE OUT switches as follows.
• Internal Gain × 200 : CAL switch "5000", VOLTAGE OUT switch "01.00"
• Internal Gain × 20000: CAL switch "0500", VOLTAGE OUT switch "10.00"
The internal gain can be calculated from the following equation.
Internal Gain = "Value of the VOLTAGE OUT switch" / "Value of the CAL switch m/m"
*When the excitation voltage is 0.5 Vrms, multiply the internal gain calculated by the above
equation by 4.

5-7-1 Setting Internal Gain with Calibration Signal

Use the calibration signal (CAL) of the DPM-900/950 series for internal gain setting.
For functions of the calibration signal, read "5-9 CALIBRATION SIGNAL."
When adjusting the sensitivity with the CAL switch "0000," neither the calibration value nor signal output
is available.
• When the measuring target is strain gage
Follows are the setting procedures of the optimum internal gain.
1) Set the DPM-900/950 series to the normal mode. (When the TEDS or ACTL LOAD switch is lighting
up, press and hold the either switch to light out.
2) Connect the strain gage and conduct bridge check.
3) Estimate the amount of the strain to be measured.
4) Set the CAL switch to the estimated amount strain.
5) Set the VOLTAGE OUT switch to the desire voltage value.
6) Press the SET switch twice.
7) Press the BAL switch twice. (The DPM-900/950 series becomes measuring state after balancing.)
While correctly setting the internal gain,
When appears on the monitor, it indicates the setting error. Read the "9-4 TROUBLE
SHOOTING.
NOTE
Set the VOLTAGE OUT switch within the range of "1.00" to "10.00" for excitation voltage 2
Vrms and "0.10" to "10.00" for excitation voltage 0.5 Vrms. Setting internal gain outside this
range may not satisfy the specification.
When the internal gain is set with the CAL switch "0000,"
voltage out is 0 V fixed regardless of the input. (The same thing happened when the range is set
to OFF with the DPM-700 series.)
appears on the monitor.
appears on the monitor and the
21