|Ames Balance Calibration Lab|
|› Ames Bal Cal Lab Home|
|› Balance Basics|
|› Tech Notes|
|› Photo Gallery|
|Ames Bal Cal Lab Contacts|
|If you would like to do business with the Balance Calibration Laboratory at Ames, please visit our contact page.|
|› Back to ARC Wind Tunnel Division|
Perform this task if there are no useful balance calibration shunt values.
Following procedure assumes balance connected to facility taper pin block.
- No load on balance (bare balance preferred)
- Balanced allowed to warmup at least 1 hour
- No touching on balance
- Use a precision/accurate voltmeter such as HP3458A
Use a stable DC power supply such as HP6612B
SDS balance channel can be used for excitation, but don't connect signal leads
- Do not connect any other signal measurements such as SDS balance amplifier signal input (it will alter measured signal).
- Voltmeter: HP3458A (note ECN and calibration date)
- DC Power Supply: HP6612B (note ECN)
Set HP3458A to 100 PLC. Do an autocal on HP3458A.
Allow enough time for voltmeter to settle on a measured signal. DVM typically displays results in millivolts.
1. Measure excitation at taper pin block on +/- SENSE connection.
2. Measure "No Load Zero" on +/- signal at taper pin block with no shunt applied.
3. Apply shunt resistor across -Exc and -Sig at taper pin block.
4. Measure "Shunt Applied" on +/- signal at taper pin block.
5. Subtract "No Load Zero" value from "Shunt Applied" value.
This is the shunt calibration value in mV (multiply by 1000 to express in uV).
6. Divide shunt calibration value by measured excitation, multiply result by 1000.
This is the normalized shunt calibration value in uV per volt.
Reason for expressing shunt calibration value normalized in uV per volt is data reduction matrix is usually formatted
in uV per volt.
Record balance model, serial number, ECN, and applicable test. Shunt resistors should always be stored with balance.
||Exc, Volts||No Load Zero, mV||Shunt Applied, mV||Shunt - No Load, mV||
Normalized shunt calibration
(shunt-no load)/exc, uV/Volt
Values on last column are the zero corrected calibration shunt values to be used in Balance Constant Conversion Form, Line F. These numbers were normalized as typical of units from Ames Balance Calibration Lab.