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PTC5000 / PTC10000 / PTCEVAL
PRECONFIGURATION
ONBOARD ADJUSTMENTS AND CONTROLS
Onboard controls are accessed on the top panel of the PTC and
must be set according to the operation mode. The controls are
illustrated in Figure 4.
Sensor Bias Current Switches (Left = On)
External / Onboard Setpoint (Left = External)
Remote / Local Output Enable (Right = Remote)
Output Enabled LED (Green = On)
Current Limit (% of Full Scale, 3/4-turn)
Onboard Temp. Setpoint Adjust (12-turn)
Proportional Term Adjust (3/4-turn)
TEMPERATURE
CONTROLLER
OUTPUT
ENABLED
LIMIT
TEMP SET
PGAIN
10 μA
100 μA
1 mA
10 mA
Ext TEMP SET
LOCAL
ENABLE
40
0
20
40
30
40
0
100
PTC SERIES
40
Figure 4. PTC Top View
SET THE SENSOR BIAS CURRENT
Choosing the right thermistor resistance range and bias current
is important to optimize performance of your temperature control
system. Table 4 shows the resistance at 25°C of six thermistors
that are available from Wavelength Electronics.
Four DIP switches are used to set the bias current driven to the
temperature sensor.
• Set the sensor bias current by sliding the appropriate switch
to the left (ON) position. All other bias current switches must
remain in the right (OFF) position.
• For AD590 temperature sensors, all sensor bias switches
must remain in the right (OFF) position.
• If you are using a 10 kΩthermistor, set the 100 μA switch to
the left (ON) and leave the others to the right (OFF).
• If multiple switches are ON, the bias currents are additive.
Table 4. Temperature Ranges of Common Thermistors
THERMISTOR
MODEL NO.
R @
25ºC 10 μA 100 μA
TCS605 5 kΩ-55 to 2°C -20 to 33°C
TCS610,
TCS10K5
10 kΩ-45 to 13°C -8 to 50°C
TCS620 20 kΩ-35 to 28°C 6 to 69°C
TCS650 50 kΩ-18 to 49°C 25 to 92°C
TCS651 100 kΩ-6 to 67°C 41 to 114°C
CHOOSE EXTERNAL VS. ONBOARD SETPOINT
The PTC includes a 12-turn trimpot for onboard temperature
setpoint control, or you can use an external signal.
• External Setpoint. Set the Ext TEMP SET switch on the
top of the unit to the left (EXTERNAL).
• Onboard Setpoint. Set the Ext TEMP SET switch on the
top of the unit to the right (ONBOARD).
CHOOSE REMOTE VS. LOCAL ENABLE
The PTC output can be enabled either remotely or set to an
always-on state. Set the unit for Remote Enable during setup
and configuration.
• Remote Enable
»Set the LOCAL ENABLE switch on the top of the unit to
the right (REMOTE).
»To enable the output, apply a TTL-High signal to pin 4
(High = 3.4 V or greater). To disable the output, the
signal on pin 4 must be less than 1.45 V.
• Local Enable
»Set the LOCAL ENABLE switch to the left (LOCAL).
»Be advised that the output current will be enabled at all
times while there is power to the unit.
CALCULATE THE TEMPERATURE SETPOINT
VOLTAGE
The actual temperature in degrees is not set directly on the
PTC unit. Instead, the temperature is controlled by a voltage
signal equal to the voltage drop across the sensor at the
desired temperature setpoint. Calculate the temperature
setpoint voltage as follows:
• Refer to the resistance vs. temperature table for your
thermistor or RTD and find the resistance at the desired
temperature. If you are using an AD590 or LM335, refer to
the datasheet for the temperature transfer function.
• Calculate the sensor voltage drop at the desired
setpoint temperature. This is the setpoint voltage value
on SetT MON:
»Thermistor and RTD:
V
SETPOINT = IBIAS * RTHERMISTOR
»LM335 and AD590:
V
SETPOINT = 2.730 + (0.010 * TSETPOINT)
UNDERSTAND THE PROPORTIONAL GAIN TERM
The gain value is factory-set to a common starting place that is
suitable for a wide range of thermal loads. Once the controller
is operating under normal conditions, the gain term can be
tuned for faster settling with minimal overshoot and ringing.
Refer to TN-TC01 - Optimizing Thermoelectric Temperature
Control Systems for details about setting the proportional gain
term.
