Model 331 Cryogenic Temperature Controller

Input Specifications

	Sensor Temperature Coefficient	Input Range	Excitation Current	Display Resolution	Measurement Resolution	Electronic Accuracy	Electronic Control Stability¹⁰
Diode	negative	0 V to 2.5 V	10 µA ±0.05%^{12, 13}	100 µV	10 µV	±80 µV ±0.005% of rdg	±20 µV
Diode	negative	0 V to 7.5 V	10 µA ±0.05%^{12, 13}	100 µV	20 µV	±80 µV ±0.01% of rdg	±40 µV
PTC RTD	positive	0 W to 500 W	1 mA¹⁴	10 mW	2 mW	±0.004 W ±0.01% of rdg	±4 mW
PTC RTD	positive	0 W to 5000 W	1 mA¹⁴	100 mW	20 mW	±0.04 W ±0.02% of rdg	±40 mW
NTC RTD	negative	0 W to 7500 W	10 µA ±0.05%¹⁴	100 mW	40 mW	±0.1 W ±0.04% of rdg	±80 mW
Thermocouple	positive	±25 mV	NA	1 µV	0.4 µV	±1 µV ±0.05% of rdg¹⁵	0.8 µV
Thermocouple	positive	±50 mV	NA	1 µV	0.4 µV	±1 µV ±0.05% of rdg¹⁵	0.8 µV
¹¹ Control stability of the electronics only, in an ideal thermal system ¹² Current source error has negligible effect on measurement accuracy ¹³ Diode input excitation current can be set to 1 mA – refer to the Model 331 user manual for details ¹⁴ Current source error is removed during calibration ¹⁵ Accuracy specification does not include errors from room temperature compensation

Thermometry
Number of inputs	2
Input configuration	Each input is factory configured as either diode/RTD or thermocouples
Isolation	Sensor inputs optically isolated from other circuits but not from each other
A/D resolution	24-bit
Input accuracy	Sensor dependent – refer to Input Specifications table
Measurement resolution	Sensor dependent – refer to Input Specifications table
Maximum update rate	10 readings/s on each input (except 5 readings/s on input A when configured as thermocouple)
User curves	Room for twenty 200-point CalCurves™ or user curves
SoftCal™	Improves accuracy of DT-470 diode to ±0.25 K from 30 K to 375 K; improves accuracy of Platinum RTDs to ±0.25 K from 70 K to 325 K— stored as user curves
Math	Maximum, minimum, and linear equation (Mx + B) or M(x + B)
Filter	Averages 2 to 64 input readings

Sensor Input Configuration

	Diode/RTD	Thermocouple
Measurement type	4-lead differential	2-lead, room temperature compensated
Excitation	Constant current with current reversal for RTDs	NA
Supported sensors	Diodes: Silicon, GaAlAs RTDs: 100 W Platinum, 1000 W Platinum, Germanium, Carbon-Glass, Cernox™, and Rox™	Most thermocouple types
Standard curves	DT-470, DT-500D. DT-670, PT-100, PT-1000, RX-102A, RX-202A	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	Two on 331S, one on 331E
Control type	Closed-loop digital PID with manual heater output, 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)	0 to 1000 with 0.1 setting resolution
Integral (reset)	1 to 1000 (1000/s) with 0.1 setting resolution
Derivative (rate)	1 to 200% with 1% resolution
Manual output	0 to 100% with 0.01% setting resolution
Zone control	10 temperature zones with P, I, D, manual heater out, and heater range
Setpoint ramping	0.1 K/min to 100 K/min
Safety limits	Curve temperature, power up heater off, short-circuit protection

Heater Output

	Loop 1	Loop 2
Heater output type	Variable DC current source	Variable DC voltage source
Heater output D/A resolution	18-bit	16-bit
Max heater power	50 W	1 W
Max heater output current	1 A	0.1 A
Heater output complaince	50 V	10 V
Heater output ranges	3 decade steps in power	1
Heater load type	Resistive	Resistive
Heater load range	10 W to 100 W recommended	100 W minimum
Heater load for max power	50 W	100 W
Heater noise (<1 kHz) RMS	50 µV + 0.01% of output voltage	<0.3 mV
Isolation	Optical isolation between output and other circuits	None
Heater connector	Dual banana	Detachable terminal block

Loop 1 Full Scale Heater Power at Typical Resistance

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Front Panel
Display	2 line by 20 character, 9 mm character height, vacuum fluorescent display
No. of reading displays	1 to 4
Display Units	K, ºC, V, mV and W
Reading source	Temperature, sensor units, max, min, and linear equation
Display update rate	All readings twice per s
Temp display resolution	0.001º from 0º to 99.999º, 0.01º from 100º to 999.99º, 0.1º above 1000º
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 for power or current
Heater output resolution	1%
Display annunciators	Control input, remote, alarm, tuning, ramp, max, min, linear
Keypad	20 full-travel keys, numeric and specific functions
Front panel features	Front panel curve entry, display brightness control, and keypad lock-out

Interfaces
IEEE-488.2 interface (331S)
Features	SH1, AH1, T5, L4, SR1, RL1, PP0, DC1, DT0, C0, E1
Reading rate	To 10 readings per s on each point
Software Support	LabVIEW™ driver (consult factory for availability)
Serial interface
Electrical format	RS-232C
Max baud rate	9600 baud
Connector	9-pin D-sub
Reading rate	To 10 readings/s on each input (at 9600 baud)
Special interface features	Model 330 command emulation mode
Alarms
Number	4, high and low for each input
Data source	Temperature, sensor units, linear equation
Settings	Source, high setpoint, low setpoint,deadband, latching or non-latching, and audible on/off
Actuators	Display, annunciator, beeper, and relays
Relays (331S)
Number	2
Contacts	Normally open (NO), normally closed (NC), and (C) common
Contact Rating	30 VDC at 5 A
Operation	Activate relays on high, low or both alarms for either input or manual
Connector	Detachable terminal block
Analog voltage output (331S)
Scale	User selected
Update rate	10 readings per s
Data source	Temperature, sensor units, linear equation
Settings	Input, source, top of scale, bottom of scale, or manual
Range	±10 V
Resolution	0.3 mV
Accuracy	±2.5 mV
Min load resistance	100 W (short-circuit protected)

General
Ambient temperature	15 °C to 35 °C at rated accuracy, 10 ºC to 40 ºC at reduced accuracy
Power requirement	100, 120, 220, 240 VAC, (+6%, -10%), 50 or 60 Hz, 120 VA
Size	216 mm W × 89 mm H × 368 mm D (8.5 in × 3.5 in × 14.5 in), half rack
Weight	4.8 kg (10.5 lb)
Approval	CE mark

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