Setting up the Cryocontroller

Introduction to the Equipment

The following is a description of the equipment necessary to run the cryomonitor for SPARO.

PC- The computer which runs the software and saves the data collected from SPARO's monitoring systems.
Computer Breakout Box- this box provides connections directly into the Labview Cards in the PC.
Thermometry Multiplexing Box(TMB)- This box basically controls which of the ROX 4-lead thermometers is being read by the lock-in based upon a two bit TTL signal from the PC.
Breakout Box #1(BB1)- This box essentially provides a patch bay for the signals coming from the Cycling Cable from SPARO.
Breakout Box #2(BB2)- This box handles all of the miscellaneous cables run through Viper's cable wrap into the control room. It provides connections from these cables to easy to handle BNC connectors.
Lock-in Amplifier- This handles the reading of the resistances of the ROX Thermometers using 4-lead techniques.
Tan HP Power supplies- One of these supplies is used to heat the charcoal pumps. The other is used to provide 24 V excitation to the He-3 pressure sensors.
Power supply for AD590's- This small green power supply is attached to the AD590 budbox and is used to provide the 10 V excitation to these temperature devices.
Blue Power Supplies- These are used to power the heaters in the Preamps.
10 microamp current source- This 9V battery powered 4-channel device is used to power the Silicon Diode Thermometers on SPARO's charcoal pumps, OVCS, and JFET boxes.

Ruthenium Oxide Thermometers

Specification sheets

The BNC connectors from Breakout Box#1(BB1) marked Detector(Inner) Stage V and I should be connected to the Thermometry Multiplexing Box(TMB) at the connectors marked V4 and I4, respectivey. Likewise The Pumped Pot V and I on BB1 should go to the TMB connectors marked V3 and I3, respectively. The TMB connections are as follows: Vout should be connected to the input A of the lock-in amplifier. Iout gets connected to the Sine out on the Lock-in through the 199.9k resistor box. TTL 1 and TTL 2 of the TMB get connected to the correspondingly labeled BNC connectors on the Computer Breakout Box and the 5V BNC on the TMB gets its power from the 5V BNC from the Computer Breakout Box.

The lock-in amplifier measures the resistance of the ROX devices using a four lead resistance measurment. The voltage the lock-in outputs to the cryocontroller PC can be converted into a resistance via the following formula:

R_T=[V_LabViewR_L/G V_{sine out}]/[1- V_LabView/(GV_{sine out})]
G is the gain the lock-in gives to the output signal. It is defined as 10/sensitivity . The standard SPARO settings for the lock-in dictate the following:

Sensitivity: 5mV
V_{sine out}: 0.040V
Time Constant: 300ms
Coupling: AC
Input: A
ground: GROUND
Reserve: Normal
Filters: Both on
R_L: 199.9 k
Frequency: 935.7 Hz
Auto-phase: on
Display: R, theta

Using this setup, the above formula reduces to:

R_T=[2500 V_LabView]/[1-(V_LabView/80)]
Note that the denominator is a small correction which takes into account that the current is limited not just by the load resistor, but also by the resistance of the device itself.

Silicon Diode Thermometers

Specification sheets

The basic setup for these thermometers is to put 10 microamps through them and measure a voltage. So for both of these thermometers, you need the battery powered 10 microamp current source(it contains 4 BNC connectors and 4 switches, and sits on the shelf in the middle of the SPARO rack). Place a BNC "T" on the current source and connect one end to BB1 at the Charcoal Pumps Silicon Diode connection. Run the other end to the Computer Breakout Box (to Channel 4). Hook up a similar connecton using one of the other channels of the current source from the OVCS diode output of BB1 to channel 6 of the Computer Breakout Box.

Charcoal Pump Heaters

Using the top HP power supply located in the middle of the rack on the shelf, run 3 BNC's in parallel. Connect one each to the two heater inputs on BB1 (Guard{outer} and Detector{inner} heaters). Run the other connection to the Computer Breakout Box, Channel 7.

³He Pressure Sensors

Power each of the two 24 V inputs of Breakout Box #2 using parallel connections from the lower HP power supply. Then, connect the signal BNC's to the Computer Breakout Box in channel 11(for the inner stage) and channel 12(for the outer stage). Set the HP power supply to 24.0 V. If you have to use the laboratory pressure sensor cables (i.e. if you are doing a cycle in the lab), the color convention is that the red wire is the 24 V excitation, the green wire gives the signal, and the white wire is the common.

Pumped Pot Pressure

In the Viper hallway, connect the Capacitance manometer readout to the capacitance manometer cable via the DB 9 connector. Then run the DC out output into the control room via a BNC. Connect this directly to the Computer Breakout Box using Channel 10.

Preamp heat

Connect the BNC's on BB2 marked preamp heat(1 and 2) to the blue power supplies located in the bottom of the rack. Note that the heat added is proportional to the square of the voltage.

Preamp Gain control

Connect TTL 3 on the Computer Breakout Box to A1 on BB2. Then connect TTL 4 on the Computer Breakout Box to A0 on BB1. The preamp gains which correspond to the TTL settings are listed below.

Gain	A1	A0
100	hi	hi
1000	hi	lo
10,000	lo	hi
100,000	lo	lo

Pump Resistor Thermometer and HWP Encoder

Connect the BNC connector from BB1 marked Pump Resistor Thermometer to an ohmmeter. Likewise, connect the output marked encoder signal to another ohmmeter.

Reading the AD590's on the Pump and Preamps

Specification sheets

The AD590 budbox is taped to a power supply. Power the budbox as marked using 10 Volts from the power supply. Connect an ammeter to the BNC on the top of the budbox(set to microamps) and connect the final BNC to the breakout connection from the AD590. For the preamps, these connections are located on BB2. For the Pump, there is a free BNC connection labeled "Pump AD590". The ammeter reading in microamps is the Kelvin temperature of the device.

Last updated: February 4, 1999 DTC