Omega Engineering CYTX231 Series, User Manual, Page: 15 / 38

Omega Model CYTX231 User’s Manual
Installation 2-3
2.3.1.2 Four-Lead Measurement
All sensors, both two-lead and four-lead
devices, can be measured in a four-lead
configuration to eliminate the effects of lead
resistance. The exact point at which the
connecting leads solder to the two-lead
sensor normally results in a negligible
temperature uncertainty.
Always use four-lead measurement configuration when a Series Platinum
Sensor is attached to the Model CYTX231P.
2.3.2 Connecting 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.
2.3.3 Sensor Mounting
Before installing a diode sensor, identify
which lead is the anode and which is the
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
silicon diode sensor lead configuration is
shown to the right. For other sensors,
read accompanying 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.
I+
V+
I–
V–
Four-Lead
Diode
CY7-SD
Diode Sensor Leads
Anode Cathode