To ensure Plate Meters accurately measure the compressed height of pasture, the counter must be calibrated. This requires setting a base level of zero so measurements can be benchmarked against this. If the counter does not return to zero after each "plonk" it will not record the measurement - hence the counter will not beep.
If the counter is removed from the black tube or receives a severe knock it may jump a groove on the steel shaft which will put the counter out of calibration. It will need to be reset.
To do this, work through the following steps:
- Ensure the plate is fully down (place on a firm flat surface) and the unit is switched off.
- Hold down the "Count" button while switching the unit on. The display will change to "CAL" briefly and display a colon ":" followed by a number. Let‘s assume you see “ : 5 “ when you switch on. Proceed as follows.
- The colon signifies that it is in fine calibration mode. Use a flat blade screwdriver and turn the blue plastic or steel shaft within the cog, anticlockwise until the display reads “ 0 “. NB: The cog and steel shaft must remain stationary.
DO NOT TURN THE SHAFT BEYOND THIS POINT OR YOU MAY DAMAGE THE POTENTIOMETER! Once the counter reads zero, move the counter up the full length of the shaft. The colon will disappear once it passes 9 and enter ‗clicks‘ mode. At full height the display should read approximately “ 52 “, which is 52 half centimetres. The counter has now been calibrated successfully.
- Switch off when you have finished, and then back on again without pressing any buttons.
- Test the zero calibration by raising and lowering the plate several times. A beep should sound and the kgDM/ha displayed as the plate falls. If it does not, repeat the steps above and retest.
If the calibration fails to hold then the potentiometer, which the cog drives is probably faulty and will need replacing. This can occur with excessive wear often compounded by dust and dirt entering the dry bearing of the potentiometer.