Model 325 Specifications

Input specifications

 Sensor temperature coefficient Input range Excitation current Display resolution Measurement resolution Electronic accuracy Electronic control stability11
Diodenegative0 V to 2.5 V 10 µA ±0.05%12, 13 100 µV10 µV±80 µV ±0.005% of rdg ±20 µV
negative0 V to 7.5 V10 µA ±0.05%12, 13100 µV20 µV±320 µV ±0.01% of rdg±40 µV
PTC RTD positive0 Ω to 500 Ω1 mA14 10 mΩ2 mΩ±0.004 Ω ±0.01% of rdg±4 mΩ
positive0 Ω to 5000 Ω1 mA14100 mΩ20 mΩ±0.04 Ω ±0.02% of rdg±40 mΩ
NTC RTD negative0 Ω to 7500 Ω10 µA ±0.05%14100 mΩ40 mΩ±0.1 Ω ±0.04% of rdg±80 mΩ
Thermocouple positive±25 mVNA1 µV0.4 µV±1 µV ±0.05% of rdg150.8 µV
positive±50 mVNA1 µV0.4 µV±1 µV ±0.05% of rdg150.8 µV

11 Control stability of the electronics only, in ideal thermal system
12 Control source error has negligible effect on measurement accuracy
13 Diode input excitation current can be set to 1 mA — refer to the Model 325 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 thermocouple

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

Measurementresolution

Sensor dependent – refer to Input Specifications table

Maximum update rate

10 rdg/s on each input (except 5 rdg/s on input A when configured as thermocouple)

User curves

Room for 15 200-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

Filter

Averages 2 to 64 input readings

Sensor input configuration

 Diode/RTDThermocouple
Measurement type 4-lead differential 2-lead, room temperature compensated
ExcitationConstant current with current reversal for RTDs NA
Supportedsensors Diodes: Silicon, GaAlAs RTDs: 100 Ω Platinum, 1000 Ω 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
Inputconnector 6-pin DIN Ceramic isothermal block

Control

Control loops

2

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 – see Input Specification 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, and heater range

Setpoint ramping

0.1 K/min to 100 K/min

Safety limits

Curve temperature, power up heater off, short-circuit protection

Loop 1 heater output

 25 Ω setting 50 Ω setting
Type Variable DC current source  
D/A resolution 16-bit
Max power 25 W  
Max current 1 A 0.71 A
Voltage compliance 25 V 35.4 V
Heater load range 20 Ω to 25 Ω40 Ω to 50 Ω
Heater load for max power 25 Ω50 Ω
Ranges 2 (2.5 W/25 W)
Heater noise (<1 kHz) 1 µV + 0.01% of output
GroundingOutput referenced to chassis ground  
Heater connector Dual banana

Loop 2 heater output

 25 Ω setting 50 Ω setting
Type Variable DC voltage source
D/A resolution 16-bit
Max power 1 W2 W
Max voltage 5 V 10 V
Current compliance 0.2 A
Heater load range ≥25 Ω≥50 Ω
Heater load for max power 25 Ω50 Ω
Ranges 1
Heater noise (<1 kHz) 50 µV + 0.01% of output
GroundingOutput referenced to chassis ground
Heater connector Detachable terminal block

Front panel

Display2- line × 20-character, liquid crystal display with 5.5 mm character height

No. of reading displays

1 to 4

Display units

K, ºC, V, mV and Ω

Reading source

Temperature, sensor units

Display update rate

2 rdg/s

Temp display resolution

0.001º from 0º to 99.999º, 0.01º from 100º to 999.99º, 0.1º above 1000º

Sensor units displayresolution

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 displayNumerical display in percent of full scale for power or current

Heater output resolution

1%

Display annunciators

Control input, Remote, Autotune

Keypad

20-key membrane, numeric and specific functions

Front panel features

Front panel curve entry, keypad lock-out

Interfaces

IEEE-488.2 interface

 

Features

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

Reading rate

To 10 rdg/s on each point

Software support

LabVIEW™ driver

Serial interface 

 

Electrical format

Baud rates

9600, 19200, 38400, 57600

Connector

9-pin D-style, DTE configuration

Reading rate

To 10 rdgs/s on each input

General

Ambient temperature

 

15 °C to 35 °C at rated accuracy, 5 ºC to 40 ºC at reduced accuracy

 

Power requirement

100, 120, 220, 240 VAC, +6%, -10%, 50 or 60 Hz, 85 VA

Size

216 mm W × 89 mm H × 368 mm D (8.5 in × 3.5 in × 14.5 in), half rack

Weight

4.00 kg (8.82 lb)

Approval

CE mark

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