soak feature (describedin detail in the next section) to test the switch. Measure-
ments can bemade by observing the display or, preferably, by collecting data
using a printeror computer connected to the RS-232 port. To set up the test do
the following steps.
1. Connect the switch wires to the terminals on the back of the dry-well and
place the switch in the well.
2. Enable set-point scanning by setting the scan to “ON” in the primary menu
(see Section 8.4.1).
3. Set the scan rate to a lowvalue, say 1.0°C/min. (see Section 8.4.2). If th e
scan rate is too high you may loseaccuracy because of transient temperature
gradients.If the scan rate istoo low the duration of the test may be longer than
is necessary.You may need to experiment to find the best scan rate.
4. Set the hold modeto automatic (see Section 8.5.2).
5. Set thescan hold to “ON” (see Section 8.5.3).
6. Set thenumber of program set-points to 2 in the program menu (see Section
8.6.1).
7. Set the firstprogram set-point to a value below the expected lower switch
temperature, say 40°C, in the program menu (see Section 8.6.2).
8. Set the second program set-pointto a value above the expected upper switch
temperature, say 90°C.
9. Set the program soak timeto allow enough time to collect a number of data
points,say 2 minutes (see Section 8.6.3).
10. Set the program function to mode 4 so that the instrument willcycle be-
tween the 2 set-points repeatedly.(See Section 8.6.4.)
11. Start theprogram (see Section 8.6.5).
12. Collectdata on a computer connected to the RS-232 port. Refer to Section
9 for instructions on configuringthe RS-232 communications interface. The
data may appear as shown in Figure 7. The maxima and minima are the switch
temperatures.
30 HartScientific
8Controller Operation