We introduce here answers to frequently asked questions.
Q1What methods of sensitivity calibration are available for measurement with a combination of strain-gage transducer and measuring instrument? What are their features?
Basically, there are the following four methods. Among them, the actual load calibration ensures the most accurate calibration.
Sensitivity Registered Calibration
Register calibration factor
Register rated output and rated capacity, or
Calibration by CAL Button
Actual Load Calibration
Strain Generator-based Calibration
1. Sensitivity Registered Calibration
Sensitivity is calibrated by entering to the measuring instrument (such as a conditioner), the rated output, rated capacity and calibration factor, all of which are stated in Test Data Sheet attached to each transducer. If the transducer has TEDS installed and the measuring instrument is TEDS-compatible, sensitivity is calibrated by reading TEDS in which the same data as stated in Test Data Sheet is written.
Sensitivity registered calibration is conveniently used for digital measuring instruments with built-in A-D converter and CPU.
2. Calibration by CAL Button
Sensitivity is calibrated by applying a load corresponding to the rated output through a press of the CAL button. This method is used for analog measuring instruments equipped with a CAL button.
3. Actual Load Calibration
Sensitivity is calibrated by applying a known load to the transducer that is connected to the measuring instrument.
To calibrate load cells with force or mass, “well calibrated weights” are used. This ensures most accurate calibration of load cells.
4. Strain Generator-based Calibration
In place of the transducer, a reference strain generator is connected to the measuring instrument. The strain generator applies to the measuring instrument a “strain” quantity corresponding to the rated output of the transducer.
When performing calibration, the following effects should be taken into consideration.
When the distance between the transducer and measuring instrument is long, a relay cable may be used.
In such a case, cable resistance affects measurement.
In “Sensitivity Registered Calibration” or “Calibration by CAL Button,” the effect should be compensated through calculation based on the sensor’s input resistance and cable resistance.
“Actual Load Calibration” or “Strain Generator-based Calibration” is made involving cable resistance and sensitivity (or CAL button) accuracy of the measuring instrument, thereby enabling calibration without receiving any effects of cable resistance and instrument’s sensitivity accuracy.
Parallel Connection Effect
Transducers are often connected in parallel. While transducers connected in parallel may be regarded as a single composite transducer, the resistance decreases to 1/number of transducers connected in parallel.
Thus, the output signal is affected in reverse proportion to the ratio of resistance decrease, thereby lowing accuracy.
The composite rated output of parallel transducers is calculated by averaging. Practically, however, the rated output varies between each transducer, thereby causing errors.
“Actual Load Calibration” is made involving such errors, thereby enabling accurate calibration.
Q2Do you have a product that can measure actual steering angles?
The SFA-E steering force/angle transducer can measure steering torque, steering angle, and angular velocity (Rate of angle change).
Q3Do you have unmanned operating products?
We offer RMH-310A and RMH-301B recorders for long-term unmanned measurement.