Recently a major manufacturer of small arms needed to instrument a rifle in order to measure rifle recoil with various types of ammunition. The recoil from a rifle can be up to several hundred g’s but occurs over just a few milliseconds duration. A 3-axis strain-gage type accelerometer having a full scale of 2000 g was selected and the USB2250 was chosen to interface directly to this sensor.
The accelerometer required a 10 Vdc excitation, and this was supplied to each axis from the USB2250 excitation supply. Each accelerometer axis provided a signal proportional to acceleration such that a signal of about 200 mV at 2000 g would be input into the USB2250. In fact the USB2250 has several gain stages higher than 220 mV so that 16 bits of digital resolution could be applied to just a part of the accelerometer’s full range if needed.
The manufacturer of the accelerometer provided calibration data for each axis: the zero offset and sensitivity differed slightly but scale and offset factors for the USB2250 were readily calculated from the calibration data supplied and each axis was configured to read directly in G’s.
The Easy Sense software supplied with the USB2250 allowed streaming of the data to a laptop PC via the USB port. The high sample rate possible by the USB2250 – up to 15,000 samples per second on all three input channels – allowed capture of the recoil shock profile as the rifle was fired. Please click here to find more information on the USB2250 and Easy Sense 2250 software.