Input specifications
Diode negative 0 V to 2.5 V
10 µA
±0.05%14, 15
100 µV 10 µV ±80 µV ±0.005% of rdg ±20 µV
negative 0 V to 7.5 V
10 µA
±0.05%14, 15
100 µV 20 µV ±80 µV ±0.005% of rdg ±40 µV
PTC RTD positive 0 Ω to 250 Ω 1 mA16 10 mΩ 2 mΩ ±0.004O ±0.01% of rdg ±4 mΩ
positive 0 Ω to 500 Ω 1 mA16 10 mΩ 2 mΩ ±0.004O ±0.01% of rdg ±4 mΩ
positive 0 Ω to 5000 Ω 1 mA16 100 mΩ 20 mΩ ±0.004O ±0.02% of rdg ±40 mΩ
NTC RTD negative 0 Ω to 75 Ω 1 mA16 1 mΩ
0.3 mΩ +
0.000% of rdg
±0.001 Ω ±0.04% of rdg ±0.6 mΩ
negative 0 Ω to 750 Ω 100 µA16 10 mΩ
3 mΩ +
0.001% of rdg
±0.01 Ω ±0.04% of rdg
±6 Ω
of rdg
negative 0 Ω to 7500 Ω 10 µA16 100 mΩ
20 mΩ +
0.001% of rdg
±0.1 Ω ±0.04% of rdg
±40 mΩ
of rdg
negative 0 Ω to 75000 Ω 1 µA16 1 Ω
0.15 Ω +
0.003% of rdg
±1.0 Ω ±0.04% of rdg
±0.3 Ω
of rdg
Thermocouple positive ±25 mV NA 1 µV 0.4 µV ±1 µV ±0.05% of rdg17 0.8 µV
positive ±50 mV NA 1 µV 0.4 µV ±1 µV ±0.05% of rdg17 0.8 µV
13 Control stability of the electronics only, in an ideal thermal system
14 Current source error has negligible effect on measurement accuracy
15 Diode input excitation current can be set to 1 mA – refer to the Model 331 user manual for details
16 Current source error is removed during calibration
17 Accuracy specification does not include errors from room temperature compensation
Number of inputs
Input configuration

Each input is factory configured as either diode/RTD or thermocouples

Sensor inputs optically isolated from other circuits but not from each other
A/D resolution
Input accuracy
Sensor dependent – refer to Input Specifications table
Sensor dependent – refer to Input Specifications table
Maximum update rate

10 readings per s on each input with the following exceptions: 5 readings per s when configured as 75 kΩ NTC RTD with reversal on, 5 readings per s on input A when configured as thermocouple
Automatically selects appropriate NTC RTD range
User curves
Room for 20 200-point CalCurves™ or user curves

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

Maximum and 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
Diodes: Silicon, GaAlAs
RTDs: 100 Ω Platinum, 1000 Ω Platinum, Germanium, Carbon-Glass, Cernox™, and Rox™
Most thermocouple types
DT-470, DT-500D, DT-670, PT-100, PT-1000, RX-102A,
Type E, Type K, Type T AuFe 0.07% vs. Cr,
AuFe 0.03% vs Cr,
6-pin DIN Ceramic isothermal block
Control loops
Control type
Closed-loop digital PID with manual heater output or open loop
Autotune (one loop at a time), manual PID, zones
Control stability

Sensor dependent – to 2× measurement resolution (in an ideal thermal system)
PID control settings
Proportional (gain) 0 to 1000 with 0.1 setting resolution
Integral (reset) 1 to 1000 (1000 per s) with 0.1 setting resolution
Derivative (rate) 1% to 200% with 1% setting resolution
Manual output
0% to 100% with 0.001% setting resolution
Zone control

10 temperature zones with P, I, D, manual heater out, and heater range
Setpoint ramping
0.1 K per min to 100 K per min
Safety limits Curve temperature, power up heater off, and 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 10 W
Max heater output current 1 A 1 A
Heater output complaince 50 V 10 V
Heater source impedance N/A 0.1 Ω maximum
Heater output ranges 3 decade steps in power 1
Heater load type Resistive Resistive
Heater load range 10 Ω to 100 Ω recommended 10 Ω minimum
Heater load for max power 50 Ω 10 Ω
Heater noise (<1 kHz) RMS 50 µV + 0.017% 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
Heater resistance Heater range Heater power
10 Ω Low 100 mW
Med 1 W
High 10 W
25 Ω Low 250 mW
Med 2.5 W
High 25 W
50 Ω Low 500 mW
Med 5 W
High 50 W
Front Panel

2 line by 20 character, 9 mm character height, vacuum fluorescent display
Number of reading
1 to 4
Display units
K, ºC, V, mV and Ω
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 is sensor dependent)
Heater output display Numerical or graphical display in percent of full scale for power or current
Heater output resolution
1% numeric or 2% graphical
Display annunciators Control input, remote, alarm, tuning, ramp, max, min, and linear
20 full-travel keys, numeric and specific functions
Front panel features Front panel curve entry, display brightness control, and keypad lock-out
IEEE-488.2 interface
FeaturesSH1, AH1, T5, L4, SR1, RL1, PP0, DC1, DT0, C0, E1
Reading rate To 10 readings per s on each point
Software Support
LabVIEW™ driver
Serial interface
Electrical format RS-232C
Max baud rate 9600 baud
Connector9-pin D-sub
Reading rate To 10 readings per s on each input (at 9600 baud)
Special interface features Model 330 command emulation mode
Number 4: high and low for each input
Data source Temperature, sensor units, and linear equation
SettingsSource, high setpoint, low setpoint, deadband, latching or non-latching, and audible on/off
Display, annunciator, beeper, and relays
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
Detachable terminal block
Analog voltage outputs  (when not used as control loop 2 output)

User selected
Update rate 10 readings per s
Data source Temperature, sensor units, and linear equation
Settings Input, source, top of scale, bottom of scale, or manual
Range ±10 V
Resolution 0.3 mV
Accuracy±2.5 mV
Max output power 1 W (jumper selected)
Min load resistance 100 Ω (short-circuit protected)
Source impedance 0.01 Ω
Ambient temp range

15 °C to 35°C at rated accuracy, 10 ºC to 40 ºC at reduced accuracy
Power requirements
100, 120, 220, 240 VAC (+6%, -10%), 50 or 60 Hz, 150 VA

216 mm W × 89 mm H × 368 mm D
(8.5 in × 3.5 in × 14.5 in), half rack
4.8 kg (10.5 lb)
Approval CE mark

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