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Model 54 Cryogenic Impedance Bridge and

Temperature Controller

Preliminary Specifications

UpUp Model 54 General Specifications

User Interface

Display Type: 800x480 color graphics TFT LCD with a capacitive touchscreen.

Keypad: Sealed Silicon Rubber.

Display Update Rate: 0.5 Seconds.

Input Channels

There are four input channels, each of which may be independently configured for any of the supported sensor type.

Sensor Connection: 4-wire differential. 6-pin circular snap-in Connector.

Sensor Types: Resistance, mutual-inductance, diode.

Input Configurations: See input specifications table.

Bridge Modes: Constant Voltage, Constant-Current or Passive.

Bridge type: Auto balancing ratiometric AC impedance bridge.

Excitation: 10 to 30Hz differential sine-wave.

Voltage Levels: 10mV to 10µV. Minimum excitation current is 1.0nA, maximum is 10mA.

DC Offset: <1nA by active cancellation

Sample Rate: 256Hz per channel.

Digital Resolution: 24 bits.

Measurement Drift:15ppm/°C. <10Ω or >10KΩ: 30ppm/°C.

Isolation: Input channel circuits are electrically isolated from all other internal circuitry but not from each other.

Measurement Filter: 2, 4, 8, 16, 32 and 64 Seconds.

Calibration Curves: Built-in curves for industry standard sensors plus eight user curves with up to 200 entries each. Interpolation is performed using a Cubic Spline.


Status Outputs

Audible and Visual Alarms: Independent audible remote and visual alarms.

Relays: Two dry-contact relays. N.O. contacts available. Ratings are 125VAC @ 10A. Maximum switching power: 150W.

Status reported via Remote Interface: Sensor fault, Heater over temperature fault, fan fault.

Control Outputs

Number of Independent Control Loops: Four.

Control Input: Any sensor input.

Loop Update Rate: 1.024KHz per loop.

Control Type: PID table, Enhanced PID, Ramp or Manual.

Isolation: Control loop circuitry is referenced to chassis ground.

PID Tables: Six user PID tables available for storage of setpoint and heater range vs. PID and heater range. 16 entries/table.

Set-point Accuracy: Six+ significant digits.

Fault Monitors: Control loops are disconnected upon detection of a control sensor fault, fan fault or excessive internal temperature.

Over Temperature Disconnect: Heater may be relay disconnected from user equipment when a specified temperature is exceeded on any selected input.

Loop #1 Control Output

Type: 75-Watt short circuit protected linear current source.

Ranges: Four output ranges of 75W, 50W, 5.0W and 0.5W into 50Ω.

Resolution: 24-bits

Readbacks: Heater output current, voltage, heatsink temperature.

Connection: Detachable terminal block.

Loop #2 Control Output

Type: Short circuit protected linear current source.

Ranges: Three output ranges of 10W, 1.0W and 1.0W into 50Ω or 25W into 25Ω.

Resolution: 24 bits.

Readbacks: Heater output power, Heatsink temperature.

Connection: Detachable terminal block.

Loop #3 Control Output

Short circuit protected linear current source.

Ranges: Two ranges of 1.0W into 100Ω.

Resolution: 24 bits.

Connection: Detachable terminal block.

Loop #4 Analog Output

Voltage outputs that can be configured as control loops or scaled analog outputs.

Output: zero to 10 / 5.0-Volts. Output impedance: ~2,000Ω.

Resolution: 24 bits.

Connection: Detachable terminal block.

Remote Interfaces

Maximum reading rate for all interfaces is >40 rdg/s.

Ethernet: Connects to any Ethernet Local Area Network. Electrically isolated. TCP/IP server provides remote control by using an ASCII command language. HTTP and HTTPS provide built-in web server. SMTP sends e-mail based on alarm conditions. EPICS CA server. Built-in firewall.

USBB: Serial port emulator.

2x USBA: External memory, mouse, keyboard.

IEEE-488.2 (GPIB): External Option, field installable.

Remote Programming Language: SCPI compliant.

LabVIEW™ drivers available for all interfaces.

Data Logging

Data logging is performed to an internal, 1,000 entry circular buffer and is time-stamped with a real-time clock. Buffer memory is non-volatile and will retain valid data without AC power.


Instrument firmware can be updated in the field via the Ethernet connection. Firmware updates are available via the Internet free of charge.


Microprocessor: 32-bit ARM9, 450Mhz.

OS: Embedded Linux, Kernel version 4.5.

Signal Processor: Cryo-con proprietary implementation using a Field Programmable Gate Array.


Ambient Temperature: 25°C ± 5°C for specified accuracy.

Mechanical: 8.5”W x 3.5”H x 12”D. One half-width 2U rack. Instrument bail standard, rack mount kit optional.

Weight: 9 Lbs.

Power Requirement: 100, 120, 220 or 240VAC +5% -10%. 50 or 60Hz, 150VA.

Conformity: European CE, RoHS compliant, Lead-free.

Calibration: NIST traceable.


UpUpModel 54 Supported Sensors

A unique feature of the Model 54 is the use of a ratiometric AC resistance bridge to measure all types of sensors.

The AC excitation used with all resistor sensors (including Platinum RTDs) is a 1.625Hz bipolar square wave. This effectively eliminates DC offset errors including the thermal EMF induced offsets that often occur in cryogenic systems.

Positive Temperature Coefficient (PTC) resistor sensors including Platinum and Rhodium-Iron RTDs use the resistance bridge in it's constant-current, AC operating mode. Platinum RTD sensors use a built-in DIN standard calibration curve that has been extended to 14K for cryogenic use.

The Model 54's resistance bridge is used in a constant-voltage AC mode to provide robust support for the Negative Temperature Coefficient (NTC) sensors commonly used by cryogenic applications. They include Ruthenium-oxide, Carbon-Glass, Cernox™, Carbon Ceramic, Germanium and several others. Since these sensors have a negative temperature coefficient, the use of a constant-voltage measurement method will reduce, rather than increase, power dissipation in the sensor as temperature decreases. By maintaining the lowest possible power level, sensor self-heating is minimized and useful temperature range is greatly increased.

An additional advantage to constant-voltage excitation is that NTC resistors lose sensitivity in the upper part of their range. By auto-ranging excitation current to maintain a constant voltage, sensitivity and noise immunity in that range is also improved.

The excitation source in the Model 54 is continuously variable so there are no steps in sensor self-heating.

Diode sensors are supported over their full temperature range by using the bridge in a DC, constant-current mode. This mode provides the required 10µA DC sensor excitation and 0 to 2.25 volt input range

Model 54 Supported Sensors
Temperature Range
Example Sensors
Diode 1.4 - 500K Cryo-con S950 / S900
SI-440, 430, 410
Lakeshore DT-670, 470
Platinum RTD 14 - 1200K Cryo-con CP-100
Cryo-con GP-100
Cryo-con XP-100
Cryo-con XP-1K
Rhodium-Iron 1.4 - 800K Oxford PHZ 0002


4K to 300K

Vishay CLTS-2B

Germanium 50mK - 100K Lakeshore GR-200A
Carbon Glass™ 1.4 - 325K Lakeshore CGR-1-500
Cernox™ 100mK- 325K Lakeshore, all types
Carbon-Ceramic 100mK - 300K TMi-A1
Ruthenium-Oxide 50mK - 200K SI RO-600


Model 54 Input Specifications

Diode sensors


Input Configuration
Constant-Current DC
Autoranging Constant-Voltage
AC Resistance Bridge
Constant-Voltage AC Bridge
Input Range
Minimum: 0.01Ω
Maximum: 500KΩ
Minimum: 16μH
Maximum: 1.6mH
Accuracy: % Rdg ± % Range
0.005% ± 80μV
0.01Ω to 30KΩ: 0.05% ± 0.04%
5Ω to100KΩ: 0.15% ± 0.15%
0.05% ± 0.04%
Resolution: % Range
10µA DC
10mV to10uV
10mA to 1.0nA,
12 to 30Hz

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Specifications subject to change without notice. ©Cryogenic Control Systems, Inc. 1998 - 2021