The Varian Thermocouple Vacuum Gauge Tube Model 531

Principles of Operation

Thermocouple gauges measure pressure in terms of the amount of heat that gas will conduct away from a hot wire. The sensing element is a combination heater and thermocouple. Cross-shaped, it is formed by joining two short resistance wires of different compositions, a method of construction which gives excellent shock resistance and yet provides the minimum mass required for fast response. With a fixed heater power, the temperature of the junction, which depends on the conductivity of the gas, is indicated by the voltage output of the thermocouple. As the pressure drops, the thermocouple gets hotter and its output increases. Readout is accomplished on a millivolt meter calibrated to indicate pressure.

General Description

The Model 531 Thermocouple Vacuum Gauge provides continuous and accurate indication of total pressure from 1 x 10^-3 to 2 Torr absolute. Developed to combine rugged dependability and outstanding performance, the 531 offers fast response and low power drain.

Specifications

Filament Current       165 mA (gives 14 mV across the thermocouple at
                      pressures below 10 -3 Torr)
Response Time          3 sec. (10 -3 to 1.0 Torr) 
Range                  1 x 10 -3  to 2 Torr 
Output                 0 to 14mV
Heater Resistance      1.4 ohms (approx.) 
Dimensions             1.21" O.D. x 3" long
Connections            May be soldered into a system, used with 1/2" '0' ring
                     compression seal or threaded on 1/8" IPS female thread.
Cable Connection       Octal Base (std.)
Casing                 Nickel-plated mild steel 
Pins                   Nickel-iron alloy (Ni 48%, Fe 52%)
Volume/Weight          12cc/2oz.

• Thermocouple Gauge Controller

Part No.	Description	UOM	ship wt.	Quantity In Stock	Price	Quantity to order
F0472301	Varian 531 Vacuum Gauge Tube (Finnigan #00105-02000)	EA	0.25	6	$62.00
Ordering information. International (non-US) prices available through your local dealer.

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