Omega Speaker Systems Stud Sensor CY670 Series User Manual

CY7/670 Series Temperature Sensors  
Application Notes  
M-4447/0307  
An excessive heat flow through the connecting  
leads to any temperature sensor can create a  
situation where the active sensing element (for the  
CY7/670 series this is the diode chip) is at a  
different temperature than the sample to which the  
sensor is mounted. This is then reflected as a real  
temperature offset between what is measured and  
the true sample temperature. Such temperature  
errors can be eliminated by proper selection and  
installation of the connecting leads.  
INSTALLATION AND OPERATION  
Three aspects of using a temperature sensor are  
critical to its optimum performance:  
the proper electrical and thermal installation of  
the connecting leads that run to the sensor  
the actual mounting of the sensor to the sample  
assembly  
the measurement electronics used for reading  
and recording temperature data from the sensor  
In order to minimize any heat flow through the  
leads, the leads should be of small diameter and  
low thermal conductivity. Phosphor-bronze or  
manganin wire is commonly used in sizes 32 or 36  
AWG. These wires have a fairly poor thermal  
conductivity yet the resistivities are not so large as  
to create any problems in four-wire  
Connecting Leads  
Although the majority of the CY7/CY670 series  
sensors are two-lead devices, measurements are  
preferably made using a four-wire configuration to  
avoid all uncertainties associated with lead  
resistance. This is done by using four connecting  
leads to the device and connecting the V+ and I+  
leads to the anode and the V– and I– leads to the  
cathode as shown in Figure 1. The exact point at  
which the connecting leads are soldered to the  
device leads results in negligible temperature  
measurement uncertainties.  
measurements.  
Lead wires should also be thermally anchored at  
several temperatures between room temperature  
and cryogenic temperatures to guarantee that heat  
is not being conducted through the leads to the  
sensor. A final thermal anchor at the sample itself  
is a good practice to assure thermal equilibrium  
between the sample and the temperature sensor.  
Note that the CU, CY, SO, and DI mounting  
adapters serve as their own sample thermal  
anchor.  
In a two-wire measurement configuration, the  
voltage connections (point A in Figure 1) are made  
near or at the current source, so only two leads  
are actually connected to the device. Some loss in  
accuracy can be expected since the voltage  
measured at the voltmeter is the sum of the diode  
voltage and the voltage drop across the  
connecting leads. The exact temperature  
uncertainty will depend on the temperature range  
and lead resistance. For a 10-ohm lead  
resistance, the diode voltage will be offset by 0.1  
mV, which gives a negligible temperature error at  
liquid helium temperature but a 50 mK error near  
liquid nitrogen temperature. Note the PI and CY  
adapter can be used only in a two-wire  
I the connecting leads have only a thin insulation  
such as vinyl acetal or other varnish type coating,  
a simple thermal anchor can be made by winding  
the wires around a copper post or other thermal  
mass and bonding them in place with a thin layer  
of CYAV varnish. There are a variety of other  
ways in which thermal anchors can be fabricated;  
a number of guidelines can be found in detail in  
the following references.  
configuration.  
Figure 1. Four-Wire Configuration for CY7/670 Series Sensor Installation  
 
CY7/670-LR  
The gold-coated copper LR adapter is designed  
3. Lift the edge of the clip using a small pair of  
pliers or screwdriver.  
for insertion into a 1/8-inch diameter tube. A thin  
layer of CYAG grease should be applied to the  
copper adapter before insertion. This eases  
installation at room temperature and enhances the  
thermal contact.  
4. Slide the SD package into place underneath  
the clip and gently lower the clip onto the lid of  
the SD package. Note that a slot is cut  
underneath the clip to accept the SD package.  
Refer to the drawing for details.  
If the device is to be used only below 325 K, a  
layer of CYAG grease should be used between  
the SD package and mounting surface to enhance  
the thermal contact.  
CY7/670-CU/DI/CY  
The gold-coated copper CU, DI and CY adapters  
serve as both a sensor and a thermal anchor  
assembly. These adapters are designed to be  
mounted to a flat surface using a 4-40 brass  
screw. Avoid over-tightening the screw; use only  
enough force to firmly hold the sensor in place.  
Brass is recommended for the screw as the  
differential thermal contraction between the  
adapter and the screw will cause the mounting  
assembly to tighten as opposed to loosen when  
the system is cooled. A thin layer of CYAG grease  
should be used to enhance the thermal contact  
between the adapter and the mounting surface.  
Sensor Operation  
Temperature controllers and thermometer  
instrumentation offered by Omega Engineering,  
Inc. are designed to be directly compatible with the  
CY7/670 series sensor to give optimum  
performance and accuracy together with direct  
temperature readouts. Simply follow the  
instructions provided with the instrument  
concerning sensor connection and instrument  
operation. If a user-supplied current source,  
voltmeter, or other instrumentation is going to be  
used with the CY7/670 series sensor, special  
attention should be given to the following details.  
The CU adapter has four color-coded leads: red  
(I–), green (V–), clear (V+), and blue (I+). The CY  
adapter has two color-coded leads: yellow (+) and  
green (–). The green lead on the DI adapter is the  
cathode.  
The CY7/670 series sensors are designed to  
operate at a constant current of 10 µA while the  
voltage variation with temperature measurement  
depends directly on the specifications of the  
current source and the voltmeter. A current source  
operating at the level of +0.01 µA (±0.01 K) is  
probably suitable for most applications. The  
voltmeter resolution required can be estimated  
from the sensitivity (dV/dT) of the CY7/670 sensor:  
CY7/670-ET/MT  
Both adapters are gold-plated copper hex head  
bolts with the SD package mounted in a slot on  
the adapter head. The ET adapter screws into a ¼  
inch deep, 6-32 threaded hole while the MT  
adapter screws into a 6 mm deep, 3 × 0.5 mm  
threaded hole. Before assembly, the threads  
should be lightly greased with CYAG grease. Do  
not over-tighten, since the threads are copper and  
can be easily sheared. Finger-tight should be  
sufficient.  
Temperature  
Sensitivity  
(mV/K)  
2.4  
(K)  
305  
77  
1.9  
4.2  
33  
Multiplying the above sensitivity by the desired  
temperature resolution in K will give the required  
voltage resolution in mV.  
CY7/670-BO  
The BO adapter should be mounted in the same  
manner as the CU. The BO adapter contains its  
own thermal anchor and is an epoxy-free  
assembly.  
The static impedance of the CY7/670 series  
sensor operating at 10 µA current is on the order  
of 100,000 ohms. Therefore, the input impedance  
of the voltmeter must be significantly larger than  
this to avoid measurement errors. Voltmeters with  
input impedances of greater than 109 or 1010  
ohms should be used.  
CY7/670-CO  
The CO adapter is used to attach the CY7/670-SD  
package to a flat surface. The adapter is a spring-  
loaded clamp designed to maintain pressure on  
the SD package as the temperature is varied.  
Good quality instrumentation must be used and all  
instrumentation and wiring should be properly  
grounded and shielded. Temperature  
measurement errors will result if there is excessive  
AC noise or ripple in the circuitry. Further details  
can be found in the article by Krause and Dodrill  
given in the references.  
1. Remove the hold down cap that holds the  
three-piece CO assembly together. The CO  
assembly should appear as shown in the  
accompanying drawings.  
2. Bolt the assembly into a 4-40 threaded hole.  
The stop on the brass screw should rest  
against the mounting surface and it also  
prevents overcompressing the spring.  
Note: All materials mentioned above that are used  
in sensor installation are available from OMEGA  
Engineering, Inc.  
3
 
REFERENCES  
Krause, J.K. and Swinehart, P.R. (1985). Demystifying Cryogenic Temperature Sensors. Photonics Spectra. August, 61–68.  
Krause, J.K. and Dodrill, B.C. (1986). Measurement System Induced Errors in Diode Thermometry. Review of Scientific  
Instruments 57 (4), 661–665.  
Sparks, L.L. (1983). Temperature, Strain, and Magnetic Field Measurements. In Material at Low Temperatures, Ed. By R.P. Reed  
and A.F. Clark. American Society of Metals, Metals Park, 515–571.  
White, G.K. (1979). Experimental Techniques in Low Temperature Physics. Clarendon Press, Oxford.  
CY7/670-SD  
CY7/670-ET  
CY7/670-BO  
CY7/670-CU/DI  
Basic sensor soldered onto SAE-  
threaded copper adapter.  
Temperature range: 1.4 to 325 K  
Mass: 1.4 g  
Basic sensor mounted into  
bolt-on disk with leads thermally  
anchored to disk with low  
temperature epoxy. CU version is  
4-lead. DI is 2-lead.  
Basic sensor package style.  
Temperature range: 1.4 to 475 K  
Mass: 0.03 g  
Basic sensor soldered onto bolt-on  
copper block with leads thermally  
anchored to block.  
Temperature range: 1.4 to 325 K  
Mass: 1.5 g  
Temperature range: 1.4 to 325 K  
Mass (excluding leads): 4.3 g  
CY7/670-CO  
CY7/670-CY  
CY7/670-LR  
CY7/670-MT  
Basic sensor soldered into  
cylindrical copper adapter.  
Temperature range: 1.4 to 325 K  
Mass: 0.15 g  
Basic sensor with spring-loaded  
brass clamp to hold sensor to  
sample.  
Temperature range: 1.4 to 475 K  
Mass (without sensor): 1.7 g  
Basic sensor soldered into metric-  
threaded copper adapter.  
Temperature range: 1.4 to 325 K  
Mass: 1.4 g  
Basic sensor epoxied into  
relatively large copper disk. 30  
AWG stranded copper lead pair is  
thermally anchored to disk.  
Temperature range: 1.4 to 325 K  
Mass (excluding leads): 4.3 g  
Servicing USA and Canada:  
Call OMEGA Toll Free  
OMEGA Engineering, Inc.  
One Omega Drive, Box 4047  
Stamford, CT 06907-0047 U.S.A.  
Headquarters: (203) 359-1660  
Sales: 1-800-826-6342 / 1-800-TC-OMEGA  
Customer Service: 1-800-622-2378 / 1-800-622-BEST  
Engineering: 1-800-872-9436 / 1-800-USA-WHEN  
FAX: (203) 359-7700 TELEX: 996404  
EASYLINK 62968934 CABLE OMEGA  
Servicing Europe: United Kingdom Sales  
and Distribution Center  
OMEGA Technologies Ltd.  
25 Swannington Road, Broughton Astley, Leicestershire  
LE9 6TU, England  
Telephone: 44 (0455) 285520 FAX: 44 (0455) 283912  
 

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