Microscale documentation

This document describes how to use the microscale.

Powering Up

- Boot the computer.
- Open microscale.ht on the desktop.
- Turn on the scale by moving the switch to the right. The LCD should turn on in about a second, and the scale will start balancing.

Calibration

- Zero the scale, by typing z into the terminal window. The Zero value can be adjusted manually via the [ and ] keys. The zeropoint is shown on the LCD's top row.
- Place a 100mg mass on the scale, wait for it to balance (about 10 seconds).
- Adjust the slope until the readout is close to 100mg, using the + and - keys.
- Verify the calibration with a smaller mass.
- Verify the zeropoint with no weight on the scale.
- Type s in the terminal window to save the calibration. This calibration will automatically be recalled next time the scale is powered on.
- To reduce the noise during the calibration, you can reduce the gain on the scale. The gain is controlled with the , and . keys (, decreases)

Operation

- Type h into the terminal if the scale is currently sending data to the laptop.
- Select the Transfer menu, Capture Text.... If a submenu pops up, choose Stop, then repeat this step.
- Choose where you want the data saved. The current default is under My Documentsmicroscale data. The file should have a .txt extension, but that is not required.
- The scale is now ready to record. Type r into the terminal just before the sample is started. The scale will reset the seconds counter to 0 and send a header row to the screen, followed by data every second.
- When the sample is finished, type h into the terminal to stop the data.
- From the Transfer menu, choose Capture Text, Stop. The file is now ready to be moved to another computer or opened in Excel.

Data format

- Column 1 is the time since r was last pressed.
- Column 2 is the temperature in C at the interface Circuit board.
- Column 3 is the calibrated reading in milligrams.
- Column 4 is the analog reading of the flag position. 512 is "balanced". If this reading is within 524 to 500, the scale is getting a reasonably good reading.
- Column 5 is the number of counts being applied to the DAC beyond the zeropoint. It is only here so that a bad calibration can be fixed after the measurement is taken.

Notes

- The data can be made less noisy by adjusting the gain down. The cost is a slower response time.
- Gain can be adjusted on the fly during a reading with no side effects.
- The gain is saved with other calibration data when s is typed.
- It may be a good idea to write down the calibration data for a particular run, as a backup.