Model 335 specifications

Input specifications — sample calculations of typical sensor performance

 Sensor temperature coefficient Input rangeExcitation currentDisplay resolution Measurement resolution Electronic accuracy (at 25 °C)6Measurement temperature coefficientElectronic control stability1
Diodenegative0 V to 2.5 V10 µA ±0.05%2, 3 100 µV10 µV±80 µV ±0.005% of rdg (10 µV + 0.0005% of rdg)/°C ±20 µV
0 V to 10 V10 µA ±0.05%2, 31 mV20 µV±320 µV ±0.01% of rdg(20 µV + 0.0005% of rdg)/°C±40 µV
PTC RTD positive0 Ω to 10 Ω1 mA4 1 mΩ0.2 mΩ±0.002 Ω ±0.01% of rdg(0.01 mΩ + 0.001% of rdg)/°C±0.4 mΩ
0 Ω to 30 Ω1 mA41 mΩ0.2 mΩ±0.002 Ω ±0.01% of rdg(0.03 mΩ + 0.001% of rdg)/°C±0.4 mΩ
0 Ω to 100 Ω1 mA410 mΩ2 mΩ±0.004 Ω ±0.01% of rdg(0.1 mΩ + 0.001% of rdg)/°C±4 mΩ
0 Ω to 300 Ω1 mA410 mΩ2 mΩ±0.004 Ω ±0.01% of rdg(0.3 mΩ + 0.001% of rdg)/°C±4 mΩ
0 Ω to 1 kΩ1 mA4100 mΩ20 mΩ±0.04 Ω ±0.02% of rdg(1 mΩ + 0.001% of rdg)/°C±40 mΩ
0 Ω to 3 kΩ1 mA4100 mΩ20 mΩ±0.04 Ω ±0.02% of rdg(3 mΩ + 0.001% of rdg)/°C±40 mΩ
0 Ω to 10 kΩ1 mA41 Ω200 mΩ±0.4 Ω ±0.02% of rdg(10 mΩ + 0.001% of rdg)/°C±400 mΩ
10 mV
negative0 Ω to 10 Ω1 mA41 mΩ0.15 mΩ±0.002 Ω ±0.06% of rdg(0.01 mΩ + 0.001% of rdg)/°C±0.3 mΩ
0 Ω to 30 Ω300 µA41 mΩ0.45 mΩ±0.002 Ω ±0.06% of rdg(0.03 mΩ + 0.0015% of rdg)/°C±0.9 mΩ
0 Ω to 100 Ω100 µA410 mΩ1.5 mΩ±0.01 Ω ±0.04% of rdg(0.1 mΩ + 0.001% of rdg)/°C±3 mΩ
0 Ω to 300 Ω30 µA410 mΩ4.5 mΩ±0.01 Ω ±0.04% of rdg(0.3 mΩ + 0.0015% of rdg)/°C±9 mΩ
0 Ω to 1 kΩ10 µA4100 mΩ15 mΩ + 0.002% of rdg±0.1 Ω ±0.04% of rdg(1 mΩ + 0.001% of rdg)/°C±30 mΩ ±0.004% of rdg
0 Ω to 3 kΩ3 µA4100 mΩ45 mΩ + 0.002% of rdg±0.1 Ω ±0.04% of rdg(3 mΩ + 0.0015% of rdg)/°C±90 mΩ ±0.004% of rdg
0 Ω to 10 kΩ1 µA41 Ω150 mΩ + 0.002% of rdg± 1.0 Ω ±0.04% of rdg(10 mΩ + 0.001% of rdg)/°C±300 mΩ ±0.004% of rdg
0 Ω to 30 kΩ300 nA41 Ω450 mΩ + 0.002% of rdg±2.0 Ω ±0.04% of rdg(30 mΩ + 0.0015% of rdg)/°C±900 mΩ ±0.004% of rdg
0 Ω to 100 kΩ100 nA410 Ω1.5 Ω + 0.005% of rdg±10.0 Ω ±0.04% of rdg(100 mΩ + 0.002% of rdg)/°C±3 Ω ±0.01% of rdg
Thermocouple positive±50 mVNA1 µV0.4 µV±1 µV ±0.05% of rdg5(0.1 µV + 0.001% of rdg)/°C±0.8 µV

1 Control stability of the electronics only, in ideal thermal system
2 Current source error has negligible effect on measurement accuracy
3 Diode input excitation can be set to 1 mA
4 Current source error is removed during calibration
5 Accuracy specification does not include errors from room temperature compensation
6 Accuracy at Tcal, typically 23.5 °C ±1.5 °C; with current reversal enabled for RTD


Number of inputs2
Input configurationInputs can be configured from the front panel to accept any of the supported input types. Thermocouple inputs require an optional input card that can be installed in the field. Once installed, the thermocouple input can be selected from the front panel like any other input type.
IsolationSensor inputs optically isolated from other circuits but not each other
A/D resolution 24-bit
Input accuracySensor dependent, refer to Input Specifications table
Measurement resolutionSensor dependent, refer to Input Specifications table
Maximum update rate10 rdg/s on each input, 5 rdg/s when configured as 100 kΩ NTC RTD with reversal on
AutorangeAutomatically selects appropriate NTC RTD or PTC RTD range
User curvesRoom for 39 200-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
MathMaximum and minimum
Filter Averages 2 to 64 input readings

Sensor input configuration

Measurement type 4-lead differential 2-lead differential, room temperature compensated
ExcitationConstant current with current reversal for RTDs NA
Supported sensors
Diodes: Silicon, GaAlAs
RTDs: 100 Ω Platinum, 1000 Ω Platinum, Germanium, Carbon-Glass, Cernox®, and Rox™
Most thermocouple types
Standard curves DT-470, DT-670, DT-500D, DT-500-E1, 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 Screw terminals in a ceramic isothermal block


Control outputs 2
Heater Outputs
Control type Closed loop digital PID with manual heater output or open loop; warm-up mode (output 2 only)
Update rate10/s
TuningAutotune (one loop at a time), PID, PID zones
Control stability Sensor dependent – see Input Specifications table
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, heater range, control channel, ramp rate
Setpoint ramping 0.1 K/min to 100 K/min

Output 1

TypeVariable DC current source
Control modes Closed loop digital PID with manual output or open loop
D/A resolution16-bit
 25 Ω setting 50 Ω setting
Max power75 W*  50 W  50 W  
Max current1.73 A1.41 A1 A
Voltage compliance (min)43.3 V35.4 V50 V
Heater load for max power 25 Ω25 Ω50 Ω
Heater load range 10 Ω to 100 Ω
Ranges 3 (decade steps in power)
Heater noise0.12 µA RMS (dominated by line frequency and its harmonics)
Heater connectorDual banana
GroundingOutput referenced to chassis ground  
Safety limits Curve temperature, power up heater off, short circuit protection
*75 W only available when output 2 is in voltage mode

Output 2

TypeVariable DC current source or voltage source
 Current mode  Voltage mode
Control modes Closed loop digital PID with manual output, zone, open loop Closed loop digital PID with manual output, zone, open loop, warm up, monitor out
D/A resolution15-bit16-bit (bipolar)/15-bit (unipolar)
 25 Ω setting 50 Ω setting NA
Max power25 W25 W1 W  
Max current1 A0.71 A100 mA
Voltage compliance (min)25 V35.4 V±10 V  
Heater load for max power 25 Ω50 Ω100 Ω  
Heater load range 10 Ω to 100 Ω100 Ω min (short circuit protected)
Ranges 3 (decade steps in power)NA
Heater noise0.12 µA RMS0.3 mV RMS
Heater connectorDual bananaDetachable terminal block
GroundingOutput referenced to chassis ground  
Safety limits Curve temperature, power up heater off, short circuit protection

Warm-up heater mode settings (Output 2 voltage only)

Warm-up percentage

0 to 100% with 1% resolution

Warm-up mode

Continuous control or auto-off

Monitor output settings (Output 2 voltage only)


User selected

Data source

Temperature or sensor units


Input, source, top of scale, bottom of scale, or manual
Update rate 10/s
Range±10 V
Resolution16-bit, 0.3 mV
Accuracy±2.5 mV
Noise0.3 mV RMS
Minimum load resistance100 Ω (short circuit protected)
ConnectorDetachable terminal block

Front panel


2-line by 20-character, 9 mm character height, vacuum fluorescent display
Number of reading displays
1 to 4
Display units
K, °C, V, mV, Ω
Reading source
Temperature, sensor units, max and min
Display update rate
2 rdg/s
Temp display
0.001° from 0° to 99.999°, 0.01° from 100° to 999.99°, 0.1° above 1000°
Sensor units display resolution
Sensor dependent, to 5 digits
Other displays

Sensor name, setpoint, heater range, heater output, and PID
Setpoint setting resolution
Same as display resolution
(actual resolution in sensor dependent)
Heater output display
Numeric display in percent of full scale for power or current
Heater output resolution
Display annunciators
Control input, alarm, tuning
LED annunciators
Remote, alarm, control outputs
25-key silicone elastomer keypad
Front panel features Front panel curve entry, display brightness control, and keypad lock-out




SH1, AH1, T5, L4, SR1, RL1, PP0, DC1, DT0, C0, E1

Reading rate

To 10 rdg/s on each input

Software support

LabVIEW™ driver



Emulates a standard RS-232 serial port

Baud rate



B-type USB connector

Reading rate

To 10 rdgs/s on each input

Software support

LabVIEW™ driver
Special interface featuresModel 331/332 command emulation mode



2, high and low for each input

Data source

Temperature or sensor units


Source, high setpoint, low setpoint, deadband, latching or non-latching, audible on/off, and visible on/off


Display annunciator, beeper, and relays





Normally open (NO), normally closed (NC), and common (C)

Contact rating

30 VDC at 3 A


Activate relays on high, low, or both alarms for any input, or manual mode


Detachable terminal block


Ambient temperature
15 °C to 35 °C at rated accuracy, 5 °C to 40 °C at reduced accuracy
Power requirement
100, 120, 220, 240 VAC, ±10%, 50 or 60 Hz, 210 VA

217 mm W × 90 mm H × 368 mm D; (8.5 in × 3.5 in × 14.5 in), half rack
5.1 kg (11.3 lb)
Approval CE mark, RoHS


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