Omega Engineering CYD201 and CYD208 manual Connecting Leads To The Sensor, Sensor Mounting

OMEGA Model CYD201/CYD208 User’s Manual

2.4.2Connecting Leads To The Sensor

Excessive heat flow through connecting leads to any temperature sensor may differ the temperature between the active sensing element and the sample to which the sensor mounts. This reflects as a real temperature offset between what is measured and the true sample temperature. Eliminate such temperature errors with proper selection and installation of connecting leads.

To minimize heat flow through the leads, select leads 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 low thermal conductivity, yet electrical resistance is not large enough to create measurement problems.

Thermally anchor lead wires at several temperatures between room temperature and cryogenic temperatures to guarantee no heat conduction through the leads to the sensor.

2.4.3Sensor Mounting

Before installing a diode sensor, identify		DT-470-SD
which lead is the anode and which is the		Diode Sensor Leads
cathode. When viewed with the base down
and the leads towards the observer, the
anode is on the right and the cathode is on
the left. The OMEGA CY-7-SD silicon diode
sensor lead configuration is shown to the
right. For other sensors, read accompanying	Cathode		Anode
literature or consult the manufacturer to

positively identify sensor leads. Lead identification should remain clear even after sensor installation. Record the sensor serial number and location.

On the CY-7-SD, the base is the largest flat surface. It is sapphire with gold metalization over a nickel buffer layer. The base is electrically isolated from the sensing element and leads; make all thermal contact to the sensor through the base. A thin braze joint around the sides of the SD package electrically connect to the sensing element. Avoid contact to the sides with any electrically conductive material.

When installing the sensor, make sure there are no electrical shorts or current leakage paths between the leads or between the leads and ground. If IMI-7031 varnish or epoxy is used, it may soften varnish-type lead insulations so that high resistance shunts appear between wires if sufficient time for curing is not allowed.

Slide Teflon® spaghetti tubing over bare leads when the possibility of shorting exists. Avoid putting stress on the device leads and allow for thermal contractions that occur during cooling which could fracture a solder joint or lead if installed under tension at room temperature.

2-4 Installation