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Scilogex Model MS-H280-Pro Hotplate & Stirrer
on July 5, 2013
I bought the MS-H280 Pro hotplate and stirrer to provide a temperature stabilized liquid bath to characterize semiconductor parameter change with temperature. The features I needed were digital control of temperature, built-in stirrer and an external temperature sensing probe. The MS-H280 Pro met those requirements at a reasonable price and a suitable size.
Scilogex has a promotion running for hotplates purchased during 2013 that provides a free platinum temperature sensor, a model PT1000 for the MS-H280. Adding the PT1000 sensor greatly increases the usefulness of the hotplate.
As an aside for those not familiar with how temperature control works with the MS-H280 and other similar products, the user enters a set point temperature and the hotplate tries to maintain that temperature by comparing the set point with measured temperature. The default measurement sensor is built into the hotplate heating element but there's obviously the potential for a significant difference between the heating element temperature and, for example, the temperature of water in a flask being heated. The optional platinum temperature sensor plugs into the hotplate and can be immersed in the liquid being heated so that the commanded temperature is compared with the liquid temperature, offering the potential of precise temperature control of the target.
To see how well the MS-H280 Pro controlled liquid temperature with the external probe, I heated 500 ml of distilled water in an Erlenmeyer flask with a stirring bar (200 RPM) and two temperature probes. One being the platinum control sensor and the second an Agilent E2308A thermistor connected to an Agilent 34410A digital multimeter, with logging every 10 seconds via an IEEE-488 bus to a laptop computer. I had previously verified the E2308A/32410A combination as within +/- 0.25 deg C at 0C and 100C.
I manually incremented the MS-H280 set point in 10 deg C increments from 50C to 100C with approximately 60 minutes per set point and a final 60 deg C setpoint after the 100C run. The logged data was post processed and plotted.
1) the MS-H280 LED temperature display provides the sensor reading and over the 50-100C range where I compared the results it agreed with the Agilent sensor values within 1 deg C which is the MS-H280's resolution.
2) Starting from room temperature and heating to the first setpoint of 50C, I observed about 1.5C overshoot, followed by a stable 49C plateau, with a small bit of ripple of about 0.5C peak to peak.
3) I found no overshoot on any of the subsequent 10C increments; just the 0.5C ripple. The peak temperature seems to be the set point and when the set point is approached the control algorithm turns the heating element off. The liquid temperature coasts upward a fraction of a degree and then drops, at which point the heating element is enabled. There seems to be a bit of hysteresis (desirable for control loop stability) in the algorithm.
4) I found no indication of undershoot in the 100C to 60C setpoint reduction.
All in all, I'm very pleased with the MS-H280 and external platinum sensor.