Application Note: Cooled SPMMini Temperature Stability

The short and medium term temperature stability of the Peltier cooler of the SPMMini was monitored. The Peltier is set to run at a fixed -20°C. The thermistor voltage was measured and digitized every millisecond using a PIC ADC. The ADC binning was 0.124°C. The data was read via a custom USB interface, feeding the data to display software. Data were acquired for ~5 minutes periods and repeated at ~hourly intervals throughout the day. The mean temperature and standard deviation were calculated from each 5 minute data set.

The SPM used for the test was a 3mm SPMMini (0708-018), biased to 32V (~4V over) and exposed to ambient light for the duration of the measurement, in order to have the condition of maximum current through the diode.