Model 321 Cryogenic Temperature Controller

The Model 321 temperature controller is obsolete and has been replaced by the new Model 325 temperature controller.

Input Specifications

	Sensor Temperature Coefficient	Input Range	Excitation Current	Display Resolution	Measurement Resolution	Electronic Accuracy	Electronic Control Stability⁵
Diode	negative	0 V to 2.5 V	10 µA ±0.05%	0.1 mV < 2 V 1 mV ≥ 2 V	0.04 mV	±0.2 mV ±0.002% of rdg	±0.08 mV
PTC RTD	positive	0 W to 300 W	500 µA ±0.01%	0.01 W< 200 W 0.1 W ≥ 200 W	5 mW	±0.02 W ±0.05% of rdg	±10 mW
Thermocouple	positive	±45 mV	NA	2 µV	1.5 µV	±4 µV ±0.05% of rdg⁷	±3 µV
⁵ Control stability of the electronics only, in ideal thermal system ⁷ Accuracy specification does not include errors from room temperature compensation

Thermometry
Number of inputs	1
Input configuration	Input is factory configured for diode, RTD, or thermocouple
Input accuracy	Sensor dependent – refer to Input Specifications table
Measurement resolution	Sensor dependent – refer to Input Specifications table
Maximum update rate	1 reading per s
User curves	One 97-point CalCurve™
SoftCal™	Improves accuracy of DT-470 diode to ±0.25 K from 30 K to 375 K
Filter	Averages 8 input readings

Sensor Input Configuration

	Diode/RTD	Thermocouple
Measurement type	4-lead differential	2-lead, room temperature compensated
Excitation	Constant current	NA
Supported sensors	Silicon Diodes 100 W Platinum RTD	Most thermocouple types
Standard curves	DT-470, DT-500D, DT-670, PT-100	Type E, Type K, Type T AuFe 0.07% vs. Cr, AuFe 0.03% vs Cr,
Input connector	6-pin DIN	Ceramic isothermal block

Control
Control loops	One
Control type	Closed-loop digital PID or open loop
Tuning	Autotune (one loop at a time), PID, PID, zones
Control stability	Sensor dependent – to 2× measurement resolution (in an ideal thermal system)
PID control parameters
Proportional (gain)	1 to 999
Integral (reset)	1 to 999 (999/s)
Derivative (rate)	1% to 200%
Zone control	10 temperature zones with P, I, D, and heater range
Setpoint ramping	0.1 K/min to 99.9 K/min
Safety limits	Curve temperature limits, power up heater off, short-circuit protection

Heater Output

	Loop 1
Heater output type	Variable DC current source
Heater output D/A resolution	15-bit
Max heater power	25 W
Max heater output current	1 A
Heater output complaince	25 V
Heater output ranges	2 decade steps in power
Heater load type	Resistive
Heater load range	21 W to 100 W recommended
Heater load for max power	25 W
Heater noise (<1 kHz) RMS	0.005% of full scale power
Isolation	Optical isolation between output and other circuits
Heater connector	Dual banana

Loop 1 Full Scale Heater Power at Typical Resistance

Front Panel
Display	2 line by 16 character alphanumeric LCD
Number of reading displays	1
Display Units	K, ºC, V, mV and W
Reading source	Temperature and sensor units
Display update rate	1 readings per s
Temp display resolution	0.1º
Sensor units display resolution	Sensor dependent, to 5 digits
Other displays	Setpoint, heater range, and heater output (user selected)
Setpoint setting resolution	Same as display resolution (actual resolution in sensor dependent)
Heater output display	Numerical display in percent of full scale current
Heater output resolution	1%
Keypad	20 keys, numeric and specific functions
Front panel features	Front panel curve entry, display brightness control, and keypad lock-out

Interface
Serial interface
Electrical format	RS-232C
Max baud rate	300 or 1200 baud
Connector	RJ11
Reading rate	To 1 readings per s
Special interface features	Model 320 command emulation mode
Analog voltage output
Scale	User selected
Update rate	1 readings/s
Data source	Temperature and sensor units
Range	0 V to 10 V, 1 mA maximum
Resolution	1.22 mV
Accuracy	0.04% of full scale output + measurement accuracy

General
Ambient temperature	20 °C to 30 °C at rated accuracy, 15 ºC to 35 ºC at reduced accuracy
Power requirements	100, 120, 220, 240 VAC, (+5%, -10%), 50 or 60 Hz, 65 VA
Size	216 mm W × 89 mm H × 318 mm D (8.5 in × 3.5 in × 12.5 in), half rack
Weight	2.7 kg (6 lb)

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