ACCELEROMETER MEASUREMENT (g)
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Accelerometer Measurement with the i100
The i100xx box provides 8 differential analog input voltage channels (14bit) that can be used for accelerometer measurement. For specifications, click here.
An Accelerometer is an external device that measures acceleration in G units. They contain an internal constant mA excitation current and provide a voltage output to the instruNet, which does not provide excitation.
Fig 3.18 - Accelerometer Measurement, Single-Ended Wiring
The i100xx connects directly to accelerometers and returns G units to the end user. When one selects "Accelerometer" in the "Sensor" field, an interview leads the user through the setting up of the device. One enters parameters such as maximum and minimum acceleration (G units) and mV per G sensitivity as specified on the physical package label (e.g. one enters "2" if the package label specifies 2 mV/G).
Accelerometers are set up in either single-ended or differential wiring mode. Figure 3.18 shows a single-ended configuration, yet one can implement differential by wiring as shown in Figure 3.2 and setting the "Wiring" field to differential "Vin+ - Vin-". instruNet calculates acceleration using the equations:
Vmeasure (V) = (Vin+ - Vin-) or Vin+ or Vin-
Acceleration (G) = Vmeasure / Sensitivity
Sensitivity = Vmeasure per G, as specified on package label
GF (Vmeasure per G) is a fixed value that is specified by the user in the Constants Settings area (indirectly if set via the interview), whereas Vmeasure is measured in realtime by instruNet. To do an Accelerometer measurement, you must:
1. Set the Sensor field in the Hardware settings area to Accelerometer.
2. Set the Range field in the Hardware settings area to accommodate the maximum accelerometer voltage (e.g. +/- 5V).
3. Set the GF field in the Constants settings area to the sensors sensitivity in Vmeasure per G units.
4. Set the Wiring field in the Hardware settings area to either differential "Vin+ - Vin-" (figure 3.2) or single-ended "Vin - Gnd" (figure 3.18), click here if you need more guidance setting up the software, and click here if the measured value is not correct.
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