Model 372 AC resistance bridge specifications

Measurement input

Input typeAC, 4-lead differential, resistance
Number of inputs1
Maximum channels16 (with optional scanner)
Resistance ranges22 ranges from 2 mΩ to 63.2 MΩ (excitation dependent)
Maximum update rate10 rdg/s (single range and input)
Range change settling3 s + filter settling
Channel change (scan) settling3 s + filter settling
ResolutionSensor and range dependent, refer to Measurement Input Specifications table
AccuracySensor and range dependent, refer to Measurement Input Specifications table
Temperature coefficient±0.0015%/°C of rdg
Maximum lead resistance100 Ω + 10% of resistance range per lead for current ≤3.16 mA; 10 Ω + 10% of resistance range per lead for current ≥10 mA
IsolationIsolated from chassis and heater grounds
Lead connectionsV+, V-, I+, I-, V shield, I shield, individual guards
Scanner lead connectionsV+, V-, I+, I-, for each sensor, shield common to all
Common mode rejectionMatched impedance voltage input and current output, active CMR
ExcitationSinusoidal AC current source
Excitation frequency9.8 Hz, 11.6 Hz, 13.7 Hz (default), 16.2 Hz, or 18.2 Hz
Excitation currents22 ranges from 1 pA to 31.6 mA RMS
Excitation accuracy±2% of nominal
Minimum excitation power10-18 W into 100 kΩ (see Measurement Input Specifications table for other ranges)
Typical DC bias current2 pA +1% of IExcitation (see Scanner application note for scanner performance)
Maximum DC bias current4 pA +1% of IExcitation (see Scanner application note for scanner performance)
Power up current protectionCurrent output shunted on power up
Voltage input ranges12 ranges from 2 µV to 632 mV RMS
Voltage input over-range20%
Voltage input impedance>5 × 1013 Ω
Maximum input voltage noise10 nV/√Hz at 10 Hz (see Scanner application note for scanner performance)
Range selection modesManual, voltage excitation, current excitation, autorange
Scanner modesManual or autoscan
Filter1 s to 200 s settling time, 1% to 80% filter window
Additional software featuresMin/Max reading capture, pause (3 s to 60 s) on range and/or channel change, scanner dwell time (1 s to 200 s)
Supported sensorsNTC resistive sensors including germanium, Cernox®, Rox™, PTC resistive sensors including rhodium-iron
Quadrature displayReal and imaginary
Connectors6-pin DIN (current out), 6-pin DIN (voltage in), and D6-pin DIN (current out), 6-pin DIN (voltage in), and DA-15 (scanner control)
Supported scannersLake Shore 3726 and 3708

 

Control input

Input typeAC, four-lead differential, resistance
Number of inputs1
Measurement unitsΩ, K (with temperature curve)
Resistance ranges6 ranges from 2 kΩ to 200 kΩ
Maximum update rate10 rdg/s (single range)
Range change settling3 s + filter settling
ResolutionSensor and range dependent, refer to Control Input Specifications table
AccuracySensor and range dependent, refer to Control Input Specifications table
Temperature coefficient±0.0015%/°C of reading
Maximum lead resistance100 Ω + 10% of resistance range per lead
IsolationIsolated from chassis, common to measurement input
Lead connectionsV+, V-, I+, I-, shield
Common mode rejectionMatched impedance voltage input and current output
ExcitationSinusoidal AC current source
Excitation frequency9.8 Hz, 11.6 Hz, 13.7 Hz, 16.2 Hz (default), or 18.2 Hz
Excitation currents6 ranges from 316 pA to 100 nA RMS
Excitation accuracy±8% of nominal for 316 pA and 1 nA ranges;
±2% of nominal for the other ranges
Power up current protectionCurrent output shunted on power up
Voltage input range200 µV
Voltage input over-range20%
Maximum input voltage noise20 nV/√Hz at 10 Hz
Range selection modesManual, standard autorange, and Rox™ RX-102B-RS optimized autorange
Filter1 s to 200 s settling time, 1% to 80% filter window
Additional software featuresMinimum/maximum reading capture
Supported sensorsNTC resistive sensors (optimized for Rox™ RX-102B-RS sensor)
Minimum temperatureDown to 10 mK using a Rox™ RX-102B-RS sensor in a well-designed system
Connector6-pin DIN

Temperature conversion

Sensor temperature coefficientNegative or positive
User curves25 CalCurves™ or user curves
Curve entryVia front panel or computer interface
Curve formatΩ/K, Log Ω/K
Curve interpolationCubic spline, linear

Sample heater output

Type Variable DC current source  
Control modesClosed-loop PID, PID zones, open-loop
Setpoint unitsΩ, K (with temperature curve)
D/A resolution 16-bit
Ranges 100 mA, 31.6 mA, 10 mA, 3.16 mA, 1 mA, 316 µA, 100 µA, 31.6 µA
Output compliance voltage (min)±10 V
Maximum power of output ranges1 W, 100 mW, 10 mW, 1 mW, 100 µW, 10 µW, 1 µW, 0.1 µW
Resistance range
1 Ω to 2 kΩ, 100 Ω for maximum power
Heater offset (at 0%)±0.02% of range
Heater gain accuracy±1% of setting
Heater noise<0.005% of range
IsolationIsolated from chassis ground, measurement and control inputs; shared ground with analog/still output
Heater connectorDetachable terminal block
Safety limitsCurve temperature, power up heater off, shunted with a relay on power up, short-circuit protection, compliance voltage limit detection, input temperature limit
Additional software featuresHeater power display based on user-entered resistance

Warm-up heater output

 25 Ω setting 50 Ω setting
Type Variable DC current source  
Control modesClosed loop PID, PID zones, open loop, warm-up mode
Setpoint unitsΩ, K (with temperature curve)
D/A resolution 16-bit
Maximum power 10 W 10 W
Maximum current 0.63 A 0.45 A
Voltage compliance (min)+15.8 V +22.4 V
Heater load for maximum power25 Ω50 Ω
Resistance range10 Ω to 100 Ω
IsolationChassis ground reference
Heater connectorDetachable terminal block
Safety limitsCurve temperature, power up heater off, shunted with a relay on power up, short-circuit protection, compliance voltage limit, relay disconnects output when off, input temperature limit

Analog/still output

TypeVariable DC voltage source
Control modesOpen loop, still heater, monitor output
IsolationIsolated from chassis ground, measurement and control inputs; shared ground with sample heater
Output voltage range±10 V
Maximum current100 mA
Maximum power1 W into 100 Ω
Minimum load resistance100 Ω (short-circuit protected)
Accuracy±2.5 mV
Noise (resolution)<0.003% of range
Monitor output settingsScaleUser selected
Data sourceTemperature or sensor units
SettingsInput, source, top of scale, and bottom of scale
ConnectorDetachable terminal block

Heater control

Number of control loops2 (sample heater, warm-up heater)
Update rate10/s
TuningManual PID, zone
PID control settingsProportional (gain)0.0 to 1,000
Integral (reset)0 to 10,000 s
Derivative (rate)0 to 2,500 s
Manual output0 to 100% with 0.01% setting resolution
Zone control10 temperature zones with P, I, D, manual heater out, heater range, setpoint, relays, and analog output (still)
Setpoint ramping0.001 K/min to 100 K/min
Scanner supportControl with scanned channel (reduced stability)
Control stabilityBelow 10 µK peak-to-peak at 50 mK (system dependent)

Warm-up heater mode settings

Warm-up percentage0 to 100% with 1% resolution
Warm-up modeContinuous control or auto-off

Front panel

Display8-line by 40-character (256 × 64 pixel) graphic VF display module
Number of reading displays1 to 8
Display unitsmK, K, mΩ, Ω, kΩ, MΩ
Reading sourceResistance, temperature, max, min
Display update rate2 rdg/s
Other displaysInput name, channel number, resistance range, excitation voltage, excitation current, excitation power, control setpoint, PID, heater range, heater output, and quadrature reading
Setpoint setting resolutionSame as display resolution (sensor-dependent)
Heater output displayNumeric display in percent of full scale for power or current
Display annunciatorsControl input and alarm
LED annunciatorsAutorange, excitation mode, autoscan, control outputs, remote, Ethernet status, alarm, still output
Keypad34-key silicone elastomer keypad
Front panel featuresFront panel curve entry, and keypad lock-out

Interface

IEEE-488.2 CapabilitiesSH1, AH1, T5, L4, SR1, RL1, PP0, DC1, DT0, C0, E1
Update rateTo 10 rdg/s on each input
Software supportLabVIEW™ driver
USB FunctionEmulates a standard RS-232 serial port
Baud rate57,600
ConnectorB-type USB connector
Update rateTo 10 rdg/s on each input
Software supportLabVIEW™ driver
EthernetFunctionTCP/IP, web interface, curve handler, configuration backup, chart recorder
ConnectorRJ-45
Update rateTo 10 rdg/s on each input
Software supportLabVIEW™ driver
Special interface featureModel 370 command emulation mode
Available baud rates300, 1,200, 9,600, 57,600
AlarmsNumber34, high and low for each measurement channel and the control input
Data sourceTemperature or sensor units
SettingsSource, high setpoint, low setpoint, deadband, latching or non-latching, audible on/off, visible on/off
ActuatorsDisplay annunciator, beeper, and relays
RelaysNumber2
ContactsNormally open (NO), normally closed (NC), and common (C)
Contact rating30 VDC at 2 A
OperationActivate relays on high, low, or both alarms for any measurement channel or control input, manual mode, or zone control mode
ConnectorDetachable terminal block monitor output
Diagnostic monitor outputOperationUser selects one of several analog voltage diagnostic points (must remain isolated)
Available signals1. AC voltage driving positive/negative side of current source programming resistor
2. AC voltage present on the positive/negative side of the differential input amplifier
3. AC voltage present on the output of the differential input amplifier
4. AC voltage into the measurement channel or control input AD converter
ConnectorBNC
Reference outputSignal typePhase-sensitive detector reference (must remain isolated)
Amplitude0 to +5 V nominal
WaveformSquare wave
ConnectorBNC

General

Ambient temperature15 °C to 35 °C at rated accuracy; 5 °C to 40 °C at reduced accuracy
Power requirement100, 120, 220, 240 VAC, ±10%, 50 or 60 Hz, 90 VA
Size435 mm W × 89 mm H × 368 mm D (17 in × 3.5 in × 14.5 in), full rack
Weight6.8 kg (15 lb)
ApprovalCE mark, RoHS
Scanner size135 mm W × 66 mm H × 157 mm D (5.3 in × 2.6 in × 6.2 in), plus connector clearance of 125 mm (5 in)