53A-339  Thermocouple Scanner Card

53A-339 -Thermocouple Scanner Card
OPT 1V · Add VXIbus Compatibility

• 24 channel thermocouple scanner
• Easy way to reduce the cost per channel in multi-port temperature monitoring systems
• Iso-thermal protection chamber
• Easy connect screw terminals
• Low thermal offset relays
• Designed to work with 53A-225 or 53A-226

The 53A-339 Thermocouple Scanner Card provides 24 channels of low thermal offset relays, each of which may be switched to a common scanner output and cabled to a CDS 53A-225 or 53A-226 Thermocouple Card. Several 53A-339’s, together with a 53A-225 or 53A-226, provide a very compact and cost effective method of scanning large numbers of thermocouple inputs. For example, in a single CDSbus Chassis, nine 53A-339’s might be cabled to the first 9 inputs of a 53A-226 Thermocouple Card to provide 216 channels of cost-effective thermocouple measurement in just 10 1/2 inches of rack space.

Thermocouple connections to the 53A-339 are made by means of easy connect screw terminals housed in a thermally protected chamber designed to eliminate temperature differences between any of the input terminals and the common output terminal. Eliminating these temperature differences minimizes measurement errors resulting from the thermoelectric effect between the dissimilar metal of the thermocouple wire and that of the screw terminal.

The cold junction compensation required for more accurate thermocouple measurements is provided in the 53A-225 or the 53A-226 Thermocouple Card. Performing cold junction compensation in a single location significantly reduces the cost per channel.

In order to prevent channel conflicts, hardware protection circuitry insures that one and only one channel may be closed on each 53A-339 in a 53/63 System at any point in time. Channels are randomly closed by transmitting ASCII characters from the system controller to the 53/63 series system. Selection of a channel on a card automatically deselects {opens) any other closed channel in order to prevent damage that might be caused by programming errors which would result in multiple closed channels.

Visual Built-In-Test Equipment {“BITE”) is provided by a series of LED indicators located at the front edge of the 53A-339. A lit LED indicates that the corresponding channel is closed.

24-channel 2-wire thermocouple scanner with common output bus

Maximum Switching Power, 1OW
Maximum Switching Voltage, 200V dc.
Maximum Switching Current, 0.5 A.

Contact Resistance:
Initial, <10 milliohms.
End of Reed Life, <1 Ohm.

Reed Life:
10^7 operations per channel at rated load of 10W


Scanning Rate:
Random channel selection at greater than 150 channels per second.

Note: Scanning rate will be limited to the measurement rate of the 53A-225 or 53A-226 Thermocouple Cards. System scanning rate may be increased by installing multiple Thermocouple Cards.

Signal Path Specifications:
Differential Thermal Offset, less than 10 microvolts.
Initial Signal Path Resistance, less than 600 milliohms.
End of Life Signal Path Resistance, less than 1.4 Ohms.

Thermal Offset (10 microvolts)
Measurement Error Equivalency for Selected Thermocouple Types and Temperature Ranges:
Type J, 0 to 760°C. <0.2°C.
Type K, 0 to 600°C. <0.25°C.
Type S and Type R, 250 to 900°C. < 1.1°C

Available Option:
OPT 1V. add VXIbus compatibility.

For additional thermocouple types or temperature ranges, consult standard thermocouple Reference Tables.