Brookfield Bath, Model TC-101 - Manual (Page 10)

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The Maximum Setpoint Differential (MSD) function provides additional protection
against excessive heating of the internal reservoir.
Setting Maximum Setpoint Differential (MSD) For External Probe
Values from 1 to 30 will be accepted. Outside this range will result in default to
previously entered value. Default is set to 10°C
External Probe MSD should be set to twice the maximum difference in °C found
between the internal and external probes when at the operating temperature. This
must be determined by actual use.
Example A : The operating temperature of your circulator is 95°C, the exterior bath
is measured to 85°C. The difference is 10°C, multiplied by 2, your (MSD) is 20.
Internal temp is 95°C, add the MSD, 20°C, equals 115°C. The controller will limit
the bath temperature to 115°C, as measured by the internai sensor.
Larger MSD numbers slow down the controllers settling time to reduce oscillations in
temperature. As a safety, if the external probe temperature drifts more than MSD
degrees from the internal probe, the internal probe takes over control.
MSD should be set greater than 5°C if:
1. External heat requirement is greater than 100 Watts.
2. External bath fluid is viscous or stirring is very slow.
3. Heat exchanger in the application is inefficient.
4. External probe is not inserted directly into the fluid.
5. External fluid lines are greater than 10 feet long.
MSD could be higher than 5°C if any of the above is true. Maximum limit is 30°C.
Optimizing of Maximum Setpoint Differential
CONTROL SYMPTOM EXTERNAL PROBE MSD
Response time too slow Lower the MSD number
Temp won’t stay at set temp Raise the MSD number
Temp won’t reach setpoint Usually raise the MSD number (Occasionally,
it may be necessary to lower MSD)
When Using an External Probe in Jacketed or Air Filled Vessel
To attain temperature uniformity, stir the external fluid with pumps or mix air with fans.
Also improve the efficiency of the heat exchanger. Enter the entire fluid volume (see
steps under FCN 6, Function Tuning) of your complete set up and the flow rate of the
slowest circulation point in your system.
Expect only ± 1.0°C stability with air or any medium that does not conduct heat well.
Insulate and cover entire set up to remove temperature gradients. The controller
cannot compensate for external chamber or component temperature gradients.
External Probe Hookup
The optional stainless steel external probe is
5
/
16
inch diameter, seven inches long,
and is available in cable lengths of 10, 25 or 50 feet with connector. If you have a
special application requiring a different probe shape, you can use an industry
standard probe from any RTD sensor manufacturer and wire it to the controller.
Maximum Setpoint
Differential (MSD)
Internal bath temp
— External bath temp
= °Temp difference
°Temp difference x 2 = MSD
MSD
+ Internal bath temp
heat limit to internal bath
Example A:
95°C Internal bath temp
— 85°C External bath temp
= 10°C Temp Difference
10°C x 2 = 20°C MSD
20°C MSD
+ 95°C Internal bath temp
= 115°C limit to internal bath