The Model 340 has been discontinued. Please consider the Model 350 and the Model 336.

Model 340 Specifications

Input specifications

Sample calculations of typical sensor performance

 Sensor temperature coefficient Input range Excitation current Display resolution Measurement resolution Electronic accuracy offsetElectronic control stability11
Diode 340/3462 negative0 V to 2.5 V 10 µA ± 0.05%12, 1310 µV10 µV±80 µV ±0.005% of rdg20 µV
negative0 V to 7.5 V10 µA ± 0.05%12, 1310 µV10 µV±80 µV ±0.01% of rdg20 µV
PRC RTD 340/3462 positive0 Ω to 250 Ω1 mA141 mΩ1 mΩ±0.002 Ω ±0.01% of rdg 2 mΩ
positive0 Ω to 500 Ω1 mA141 mΩ1 mΩ±0.002 Ω ±0.01% of rdg2 mΩ
positive0 Ω to 2500 Ω0.1 mA1410 mΩ10 mΩ±0.03 Ω ±0.02% of rdg20 mΩ
1 mV 340/3462
negative0 Ω to 10 Ω100 µA14100 µΩ1 mΩ±0.02% rng ±0.1% of rdg2 mΩ
negative0 Ω to 30 Ω30 µA14100 µΩ3 mΩ±0.02% rng ±0.1% of rdg6 mΩ
negative0 Ω to 100 Ω10 µA141 mΩ10 mΩ±0.02% rng ±0.1% of rdg20 mΩ
negative0 Ω to 300 Ω3 µA141 mΩ30 mΩ±0.02% rng ±0.1% of rdg60 mΩ
negative0 Ω to 1 kΩ1 µA1410 mΩ0.1 Ω±0.02% rng ±0.1% of rdg0.2 Ω
negative0 Ω to 3 kΩ300 nA1410 mΩ0.3 Ω±0.02% rng ±0.1% of rdg0.6 Ω
negative0 Ω to 10 kΩ100 nA140.1 Ω1 Ω±0.02% rng ±0.1% of rdg2 Ω
negative0 Ω to 30 kΩ30 nA140.1 Ω3 Ω±0.02% rng ±0.1% of rdg6 Ω
10 mV 340/3462
negative0 Ω to 30 Ω300 µA14100 µΩ300 µΩ±0.02% rng ±0.05% of rdg600 µΩ
negative0 Ω to 100 Ω100 µA141 mΩ1 mΩ±0.02% rng ±0.05% of rdg2 mΩ
negative0 Ω to 300 Ω30 µA141 mΩ3 mΩ±0.02% rng ±0.05% of rdg6 mΩ
negative0 Ω to 1 kΩ10 µA1410 mΩ10 mΩ±0.02% rng ±0.05% of rdg20 mΩ
negative0 Ω to 3 kΩ3 µA1410 mΩ30 mΩ±0.02% rng ±0.05% of rdg60 mΩ
negative0 Ω to 10 kΩ1 µA140.1 Ω0.1 Ω±0.02% rng ±0.05% of rdg0.2 Ω
negative0 Ω to 30 kΩ300 nA140.1 Ω0.3 Ω±0.02% rng ±0.05% of rdg0.6 Ω
negative0 Ω to 100 kΩ100 nA141 Ω3 Ω±0.02% rng ±0.05% of rdg6 Ω
negative0 Ω to 300 kΩ30 nA141 Ω30 Ω±0.02% rng ±0.25% of rdg60 Ω
Thermocouple 3464 positive±25 mV NA0.1 µV0.2 µV±1 µV ±0.05% of rdg150.4 µV
positive±50 mV NA0.1 µV0.4 µV±1 µV ±0.05% of rdg150.8 µV
Capacitance 3465positive or negative 0 nF to 150 nF 4.88 kHz 1 V square wave10 pF2.0 pF±50 pF ±0.1% of rdg4.0 pF
positive or negative 0 nF to 15 nF4.88 kHz 1 V square wave 1 pF0.2 pF±50 pF ±0.1% of rdg0.4 pF
Diode 3468 negative0 V to 2.5 V 10 µA ± 0.05%12, 13100 µV20 µV±160 µV ±0.01% of rdg40 µV
negative0 V to 7.5 V10 µA ± 0.05%12, 13100 µV20 µV±160 µV ±0.02% of rdg40 µV
PTC RTD 3468 positive0 Ω to 250 Ω1 mA ± 0.3%1410 mΩ2 mΩ±0.004 Ω ±0.02% of rdg4 m Ω
positive0 Ω to 500 Ω1 mA ± 0.3%1410 mΩ2 mΩ±0.004 Ω ±0.02% of rdg4 m Ω
positive0 Ω to 5000 Ω1 mA ± 0.3%14100 mΩ20 mΩ±0.06 Ω ±0.04% of rdg40 m Ω
NTC RTD 3468 negative0 Ω to 7500 Ω10 µA ± 0.05%14100 mΩ50 mΩ±0.01 Ω ±0.04% of rdg0.1 Ω

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


Number of inputs2 included (additional inputs optional)
Input configurationEach input is pre-configured as diode/RTD. Thermocouple and capacitance are optional and sold as additional input cards.
IsolationSensor inputs optically isolated from other circuits but not from each other
A/D resolution 24-bit analog-to-digital
Input accuracySensor dependent — refer to Input Specifications table
Measurement resolutionSensor dependent — refer to Input Specifications table
Maximum update rateUp to 20 readings/s on an input, 40 readings/s on all inputs
AutorangeAutomatically selects appropriate NTC RTD range
User curvesForty 200-point CalCurves™, or user curves
SoftCal™Improves accuracy of DT-470 diode or platinum RTD sensors
MathMaximum and minimum of input readings and linear equation
Filter Averages input readings to quiet display, settable time constant


Control loops 2
Control type Closed-loop digital PID with manual heater power output, or open loop
TuningAutotune (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 with 0.1 setting resolution
Derivative (rate) 1 to 1000 s with 1 s resolution
Manual output 0 to 100% with 0.01% setting resolution
Zone control 10 temperature zones with P, I, D, manual heater power out, and heater range
Setpoint ramping 0.1 K/min to 100 K/min
Safety limits Setpoint limit, curve temp limits, heater output, slope limit, heater range limit, power up heater off, and short-circuit protection

Heater output

 Loop 1 Loop 2
Heater output type Variable DC current sourceVariable DC voltage
Heater output D/A resolution 18-bit14-bit
Max heater power 100 W1 W
Max heater output current 2 A0.1 A
Heater output compliance50 V10 V
Heater source impedance NA0.01 Ω
Heater output ranges 5 decade steps in power1
Heater load type ResistiveResistive
Heater load range 10 Ω to 100 Ω recommended100 Ω minimum
Heater load for max power 25 Ω100 Ω
Heater noise (<1 kHz) RMS 50 µV + 0.001% of output voltage<0.3 mV
IsolationOptical isolation between output and other circuitsNone
Heater connector Dual bananaBNC

Loop 1 full scale heater power at typical resistance

Heater resistanceHeater rangeMaximum current
2 A1 A0.5 A0.25 A
10 Ω540 W10 W2.5 W625 mW
44 W1 W250 mW62.5 mW
30.4 W100 mW25 mW6.25 mW
240 mW10 mW2.5 mW625 µW
14 mW1 mW250 µW62.5 µW
25 Ω5100 W25 W6.25 W1.56 W
410 W2.5 W625 mW156 mW
31 W250 mW62.5 mW15.6 mW
2100 mW25 mW6.25 mW1.56 mW
110 mW2.5 mW625 µW156 µW
50 Ω 550 W50 W12.5 W3.12 W
420 W5 W1.25 W312 mW
32 W500 mW125 mW31.2 mW
2200 mW50 mW12.5 mW3.12 mW
120 mW5 mW1.25 mW312 µW

Extending temperature controller heater power It is often necessary to extend the heater power of a cryogenic temperature controller to conduct experiments above room temperature. This diagram illustrates a practical way to increase the control output of the Model 340 to several hundred watts. A programming resistor, Rpgm, is placed across the controller’s heater output current source. As the heater output current changes, a changing voltage is generated across Rpgm. That voltage is used to program a large external power supply. Rpgm should be chosen so that a low current range of the controller can be used. The control output of loop 2 on the Model 340 is a voltage, thus it can be connected directly to the external power supply without Rpgm.

Temperature controller heater power diagram

Sensor input configuration

Measurement type 4-lead differential2-lead, room temperature compensated4-lead
ExcitationConstant current with current reversal for RTDsNA4.88 kHz, 1 V square wave
Supported sensorsDiodes: silicon, GaAlAs RTDs: 100 Ω platinum, 1000 Ω platinum, germanium, carbon-glass, Cernox®, and Rox™Most thermocouple typesCS-501GR
Standard curvesDT-470, DT-500D, DT-670, PT-100, PT-1000, RX-102A,RX-202AType E, Type K, Type T AuFe 0.07% vs. Cr, AuFe 0.03% vs CrNone
Input connector 6-pin DINCeramic isothermal block6-pin DIN

Front panel

DisplayGraphic LCD with fluorescent backlight
No. of reading displays1 to 8
Display units Temperature in K, °C, or sensor units
Temp display resolution0.0001 K below 10 K, 0.001 K above 10 K
Sensor units display resolutionSensor dependent, to 6 digits
Setpoint setting resolutionSame as display resolution(actual resolution in sensor dependent)
Heater output displayNumeric display in percent of full scale for power or current-bar graph display of heater output available
Heater output resolution0.1% numeric or 2% graphical
KeypadNumeric plus special function
Front panel featuresFront 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 20 readings/s
Software Support National instruments LabVIEW™ driver

Serial interface

Electrical format RS-232C
Max baud rate 19,200 baud
Reading rate To 20 readings/s


Number Two, high and low, for each installed input
Data source Temperature, Sensor Units, and Linear Equation
SettingsSource, High and Low Setpoint , Latching or Non-latching, and Audible On/Off
ActuatorsDisplay, annunciator, beeper, and relays


Number 2
Contacts Normally open (NO), normally closed (NC), and common (C)
Contact rating 30 VDC at 2 A
Operation Activate relays on high or low alarms for any input, or manual off/on
ConnectorDetachable terminal block

Analog voltage outputs

(when not used as control loop 2 output)

Number 2
Scale User selected
Update rate 20 readings/s
Data source Temperature, Sensor Units, and Linear Equation
Settings Input, Source, Top of Scale, Bottom of Scale, or Manual
Range ±10 V
Resolution 1.25 mV
Accuracy±2.5 mV
Max output power 1 W
Min load resistance 100 Ω (short-circuit protected)
Source impedance 0.01 Ω

Digital I/O

5 inputs and 5 outputs — TTL voltage level compatible

Data card

PC card Type II slot used for curve transfer, setup storage, and data-logging


Ambient temp range 20 °C to 30 °C (68 °F to 86 °F) specified accuracy; 15 °C to 35 °C (59 °F to 95 °F) reduced accuracy
Power requirements 100, 120, 220, 240 VAC (+5%, -10%), 50 or 60 Hz; 190 VA
Size 432 mm W × 89 mm H × 368 mm D (17 in × 3.5 in × 14.5 in), full rack
Weight 8 kg (17.6 lb) approx.
Approval CE mark

3003 heater output conditioner

The heater output conditioner is a passive filter which further reduces the already low Model 340 heater output noise. The typical insertion loss for the Model 3003 is 20 dB at or above line frequency, and >40 dB at or above double line frequency. A 144 mm W × 72 mm H × 165 mm D (5.7 in × 2.8 in × 6.5 in) panel mount enclosure houses this option, and it weighs 1.6 kg (3.5 lb).

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