iLoad Mini Application Note
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.
| Line | USB Mini-B Connector Pin | Color | Description |
|---|---|---|---|
| 5V | Pin 1 | Red | Power Requirement: 5V +/- 5% at 5mA. |
| CTRL | Pin 2 | White |
When CTRL = High, FREQ = Cx When CTRL = Low, FREQ = Cr |
| FREQ | Pin 3 | Green | Frequency Output. |
| GND | Pin 5 | Black | Ground |
The CTRL line acts as a switch. The FREQ line outputs the Cx frequency when the CTRL line is High, and outputs the reference Cr 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.
Cx is sensor frequency and it varies with load. Cr is reference frequency used for environmental compensation. K is a constant determined by Loadstar Sensors as part of our calibration.
Cc is called the Compensated Output as defined below:
Cc = 5E6 - [10*(Cx - K*Cr )]
The formula for measuring the load (in lbs) is:
Load = qA*Cc2 + qB*Cc +
qC
With no load, calculate Load0 using the above formula. Put a known weight on the sensor and calculate Loadx. The actual weight is the difference between the 2 loads:
W = Loadx - Load0
Loadstar Sensors will provide the following constants for calibrated sensors:
| Constant | Description |
|---|---|
| K | Environmental Compensation |
| qA | Quadratic A. |
| qB | Quadratic B. |
| qC | Quadratic C. |