MINI3 Sensor Application Note

Last Update 6/19/08

The iLoad Mini is shipped with a cable that terminates in a male USB Mini-B 5-pin connector that plugs in to a Loadstar Sensors's DQ1000 family Frequency Converter interface. If you wish to use the iLoad Mini as a standalone frequency sensor, you may cut off the Mini-B connector and connect the four wires within the cable to your instrumentation. The table below identifies the color coding of the wires and the pin-out of the USB Mini-B connector.

The CTRL line acts as a switch. The FREQ line outputs the C_x frequency when the CTRL line is High, and outputs the reference C_r frequency when the CTRL line is Low.

The measuring device should have a buffered output CTRL and a buffered input FREQ as shown in the above block diagram.

C_x is sensor frequency and it varies with load. C_r is reference frequency used for environmental compensation. K is a constant determined by Loadstar Sensors as part of our calibration.

C_c is called the Compensated Output as defined below:

C_c = 5E6 - [10*(C_x - K*C_r )]      

The formula for measuring the load (in lbs) is:

Load = q_A*C_c² + q_B*C_c + q_C   

With no load, calculate Load(0) using the above formula. Put a known weight on the sensor and calculate Load(x). The actual weight is the difference between the 2 loads:

W = Load_x - Load₀.

Loadstar Sensors will provide the following constants for calibrated sensors: