Test #3 - iButton Calibration

Vancouver, B.C., Canada
June 8, 2001




Thermochron -F50s in ice bath after a few minutes.
Crushed ice would be better to maintain a temperature near 0° C,
since as the ice melts the Thermochrons are left in 4° C water.







Water bath used to measure Thermochron accuracy.
- A continuously circulating, thermostat-controlled heater.
- Unfortunately, after reaching the pre-set temperature of 45° C, the heater shut off and wouldn't come on again!
- Hence the cooling slope with "standard thermometer readings recorded manually.
- Several constant temperatures would be much better to determine any -F50 temperature offsets or variations with temperature level.

Instruments measured:
  1. "standard" mercury thermometer
  2. "standard" dial thermometer (calibrated to the mercury thermometer)
  3. -F50 Thermochron - "A"
  4. -F50 Thermochron - "C"
  5. -F50 Thermochron - "D"




Adjustable "standard" dial thermometer was precisely calibrated to the "standard" mercury thermometer.







Thermochrons were attatched, at about half-depth, to an anchored string.







Data for complete "mission".




Detail of cooling slope.


  • Results and Conclusions:
    1. The Thermochrons were on the bottom of the ice bath.
      • As the ice began to melt the 0° C water was at the surface while the Thermochrons were in the 4° C water at the bottom.
      • Stirring up the ice bath showed an expected lowering of the temperature value.
    2. The water bath was originally set to 45° C, but unfortunately the heater died so the temperature dropped.
      • Since there was a large volume, the rate of temperature drop was slow.
    3. The values for the mercury and dial thermometers were identical.
      • The dial had been calibrated to the mercury themometer.
    4. The "A" and "D" -F50's gave similar values to the "standard" thermometers.
    5. The "C" routinely gave values 0.5° to 1° C below the "standards".
      • This will have to be applied to the eclipse values.
      • It really needs an accurately controled water bath and measurements at several temperatures to determine the offset for each Thermochron unit.
    6. Rubbing the -F50s between the fingers gave a usable time marker.



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