Lake Shore 350, User Manual

Page: 84 / 192

70 c
HAPTER
4: Operation
Model 350 Temperature Controller
4.4.6.2 Temperature Coefficient Selection
Capacitance sensors can have both a positive and negative temperature coefficient
(slope). They have a positive temperature coefficient at very low temperatures and a
negative temperature coefficient at warmer temperature. Sensor data sheets detail
where the coefficient changes. There is often a temperature range where the sensor is
not usable. Temperature control is impossible if the Model 350 does not know which
slope the sensor is on. System overheating can result if the wrong coefficient is cho-
sen. The user must select a temperature coefficient before control is switched to the
capacitance input.
Menu Navigation:
Input Setup
Q
Input (D)
Q
Temp Coefficient
Q
(Negative or Positive)
Interface Command:
INTYPE
4.4.6.3 Control Channel Changes
The capacitance input continues control at a stable temperature established with
another sensor. Allow temperature to stabilize for one hour after large temperature
changes to allow capacitance sensor recovery.
When the control channel is changed to the capacitance input, the Model 350 auto-
matically changes the control setpoint to the present capacitance reading. It is not
necessary for the user to write down the capacitance value and en-ter a new setpoint.
Control parameters, P and I, may need to be changed for stable control.
4.4.7 4-Channel
Scanner Input Setup
(Model 3062 Only) When a Model 3062 4-Channel Scanner option is installed in the Model 350, 4 addi-
tional channels, D2, D3, D4, and D5, become available for use. The channels are
scanned with the Model 350's Input D at a reduced update rate. The scanner option
channels can be configured for diode, negative temperature coefficient resistor, or
positive temperature coefficient resistor sensors. Specifications for the 4-channel
scanner option are given in TABLE 4-9.
Menu Navigation:
Input Setup
Q
Input (D2, D3, D4, or D5)
Q
Sensor Type
Q
(Disabled, Diode, PTC RTD
(Platinum), NTC RTD (Cernox)
Default: Diode
Interface Command:
INTYPE
4.4.7.1 Type and Range Selection
The 4-channel scanner option can be configured as either diode, PTC RTD, or NTC RTD.
Autorange will be on by default whenever the Sensor Type parameter is set to PTC RTD
or NTC RTD. To manually select the resistance range, set the Autorange parameter to
Off , then use the Range parameter to select the desired range.
Menu Navigation:
Input Setup
Q
Input (D2, D3, D4, or D5)
Q
Autorange
Q
(Off or On)
Input Setup
Q
Input (D2, D3, D4, or D5)
Q
Range
Q
(See TABLE 4-9)
Default: On
Interface Command:
INTYPE