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ManualsBrandsOmega ManualsTemperature SensorOMEGA DT-470 Silicon Diode Temperature Sensor

CAUTION: This temperature sensor is sensitive to electrostatic discharge (ESD). Use ESD

precautionary procedures when handling, or making mechanical or electrical connections to this

device in order to avoid performance degradation or loss of functionality.

There are three aspects of using a cryogenic

temperature sensor which are critical to its

optimum performance. The first involves the proper

mounting of the sensor package, the second

relates the proper joining of sensor lead wires and

connecting wires. The final concern is the thermal

anchoring of the lead wires. Although the

sequence in which these areas should be

addressed is not fixed, all elements covered under

each aspect should be adhered to for maximum

operating capabilities of the sensor.

CAUTION: The braze ring that wraps around

the base of the sensor is electrically

connected to the positive (+) lead. Use

caution not to cause a short by letting the

braze ring come in contact with electrically-

conductive material.

SENSOR MOUNTING

1. Mounting area should be prepared and

cleaned with a solvent such as acetone

followed by an isopropyl alcohol rinse. Allow

time for the solvents to evaporate before

sensor mounting.

2. T

he list below provides brief instructions on mounting a sensor using a number of different methods. The constraints of

your application should dictate the most appropriate mounting method to follow.

Mechanical – T

he preferred method for mechanically mounting an SD sensor is using the Lake Shore spring loaded

clamp. This clamp should be ordered at the time the sensor is ordered (P/N DT-670-CO, DT-470-CO, etc.). The clamp

holds the SD sensor in contact with the surface and also allows the sensor to be easily changed or replaced. A thin layer

of Apiezon

N Grease (≤0.055 mm) or a flat 100% indium preform should be used between the sensor and mounting

surface to enhance thermal contact. The spring prevents crushing the sensor.

Indium Solder (

100% In) – A low wattage heat source should be used and the sensor must never exceed 200 °C. The

mounting surface and sensor should be tinned with a rosin flux (type RMA is recommended) prior to mounting the sensor.

A thin, uniform layer of indium solder should be the goal. Clean both the sensor and mounting surface of residual flux

using rosin residue remover. Once the surface area is dry, reheat the mounting surface to the melting point of the solder

(156 °C). Press the sensor into position and allow it to warm to the melting point of the solder. Remove heat source and

allow sufficient time for the solder to solidify (typically 2 to 3 s) before removing it.

Apiezon

N Grease – Is best used as a thermal conductor when the sensor is mounted in a hole or recess and when the

sensor is intended to be removed. The sensor should be surrounded with thermal grease and placed into the mounting

position. When the temperature is lowered the thermal grease will harden, giving good support and thermal contact.

IMI 7031 Varnish – P

repare varnish and apply a thin layer on the mounting surface. Press the sensor firmly against the

varnish during curing to ensure a thin bond layer and good thermal contact. Varnish will air dry in 5 to 10 min. Sufficient

time must be allowed for the solvents in the varnish to evaporate. There is a small probability of ionic shunting across the

sensor during the full cure period of the varnish (typically 12 to 24 h).

Stycast

2850FT Epoxy – Prepare epoxy and apply a thin layer on the mounting surface. Press the sensor firmly into the

epoxy during curing to assure a thin bond layer and good thermal contact. Epoxy will cure in 12 h at 25 °C or in 2 h at

66 °C.

3. F

ollow manufacturer’s instructions for adhesive curing schedule. Never heat the sensor above 200 °C.

Summary of content (3 pages)

PAGE 1
CAUTION: This temperature sensor is sensitive to electrostatic discharge (ESD). Use ESD precautionary procedures when handling, or making mechanical or electrical connections to this device in order to avoid performance degradation or loss of functionality. There are three aspects of using a cryogenic temperature sensor which are critical to its optimum performance. The first involves the proper mounting of the sensor package, the second relates the proper joining of sensor lead wires and connecting wires.
PAGE 2
LEAD ATTACHMENT 1. Although the DT-470/471/670/671 SD sensor package is a two-lead device, measurements should be preferably made using a four-wire configuration to avoid uncertainties associated with lead resistance. Two-lead measurement scheme – The leads used to measure the voltage are also the current carrying leads. The resultant voltage measured at the instrument is the sum of the temperature sensor voltage and the voltage drop across the two leads. See Figure 1A.
PAGE 3
CRYOGENIC ACCESSORIES – Recommended for proper installation and use of DT-470/471/670/671 SD sensors: Stycast® Epoxy 2850FT (P/N 9003-020, 9003-021): Permanent attachment, excellent low temperature properties, poor electrical conductor, low cure shrinkage. Apiezon® N Grease (P/N 9004-020): Low viscosity, easy to use, solidifies at cryogenic temperatures, excellent lubricant. IMI 7031 Varnish (P/N 9009-002): Nonpermanent attachment, excellent thermal conductor, easy to apply and remove.