Sensors

Thermocouple Sensors

This type of sensor uses two different metals for the positive and negative leads. With the probe end at a different temperature to the lead end, a voltage proportional to temperature is produced. By using electronic circuitry within the temperature controller to simulate 0 Degrees C, this voltage can be used to accurately measure temperature. Different metal configurations are chosen for their different voltage / temperature graphs. For most common plastic and general processing applications, either types J and type K are used. Type T is commonly used for food processing.

Compensating Cable

The metals used in thermocouple probes are usually of a high cost and could not be used economically for long distances. Therefore, cheaper metals with the same thermal / voltage characteristics at ambient temperatures are used to connect the probe to the controller. These are called compensating cables and must be used to prevent inaccuracies occurring.

International colour coding standards are used to identify which thermocouple type the compensating cable is for. See the Technical Documents for a downloadable chart of the international colour coding standards.

Mineral Insulated

It is common for the thermocouple junction within the probe to be connected to the body of the probe, which is then normally grounded. However, in applications where a fault condition can cause mains voltages to be passed up the thermocouple leads, mineral insulated types are available in which the thermocouple junction is insulated from the probe body.

Platinum Resistance Thermometer (PRT) Sensors

This type of sensor uses a special resistor which varies its resistance with temperature. This type of probe usually has a resistance of 100 Ohms at 0C, hence the name PRT100. Although limited in temperature range, this type of sensor is typically 10 times more accurate. The size of the sensing resistor limits the manufacture of very small probes.

Sensor Build Formats

Type: P (Basic)

Basic probe sensor with stainless steel armoured or braided lead. Various diameters available. Imperial: 1/8”, 5/32”, 3/16”, 1/4”, 5/16”, 3/8”, 7/16”, 1/2”. Metric: 3, 3.5, 4, 4.5, 5, 6, 7, 8, 10mm Tubing is normally cold-drawn grade 316 unless otherwise specified.

Specify: Dimensions A & L.

Type: R (Angled Basic)

Angled basic probe sensor with stainless steel armoured or braided lead. Various diameters available. Imperial: 1/8”, 5/32”, 3/16”, 1/4”, 5/16”, 3/8”, 7/16”, 1/2”. Metric: 3, 3.5, 4, 4.5, 5, 6, 7, 8, 10mm Tubing is normally cold-drawn grade 316 unless otherwise specified.

Specify: Dimensions A, L1 & L2.

Type: B (Leaf)

Typically used for fitting under heater bands. Stainless steel shim is 20mm x 15mm and can be cut to shape, as required. Braided cable attached directly to .25mm thick wafer. Very fast response. Different leaf dimensions available on request.

Specify: Dimension A.

Type: C (Washer)

Surface mounting thermocouple with plated copper cable lug. Bare junction spot-welded to lug. Available with different hole sizes. 6mm is available from stock. 4BA, 2BA, 4mm, 5mm diameters are available on request.

Specify: Dimensions A, d.

Type:D (Straight Nozzle)

Free-turning hexagon screw on short thermocouple probe. Available with or without strain spring relief. Thread length is 10mm unless otherwise specified.

Specify: A, Screw thread ‘t’ (6 x 1mm, 1/4” UNF-28, 1/4” BSF, 0BA, 8 x 1mm or 8 x 1.25mm).

Type: D2 (Right Angled Nozzle)

Free-turning hexagon screw on short thermocouple probe. Available with or without strain spring relief. Thread length is 10mm unless otherwise specified.

Specify: A, Screw thread ‘t’ (6 x 1mm, 1/4” UNF-28, 1/4” BSF, 0BA, 8 x 1mm or 8 x 1.25mm).

Type: G (8mm Bayonet)

Length L is 20mm unless otherwise specified. Cap has 2 slots for bayonet coupling. Internal diameter of cap is 13, 14 15, 16 or 17mm clearance. Adjustment for hole depth is by screwing cap along spring. Stainless steel braid only.

Type: H (Bayonet)

Cap and spring between fixed collars on 1.6mm ( 3/16”) tube. 11.7mm I.d. cap has single slot. Distance L from back of cap to tip of probe or from top of adaptor to bottom of hole in machine must be specified. Tube can be angled behind cap as with basic assemblies.

Type:J (Bayonet)

Length L is 10mm unless otherwise specified. Adjustment for hole depth is by screwing cap along armour, which can be compressed to act as a spring.

Type: IT (External Bayonet)

External pin bayonet assembly (Italian Design). Adjustment for hole depth is by screwing cap along spring. Stainless steel braid only.

Type: F (Band)

Band thermocouples for clamping round nozzles, cylinders and pipes. Available with stainless steel band with clamp bolt.

Specify: Dimension D, width (6mm or 10mm for clamp bolt and 12mm for jubilee clip), Entry angle (Radial, Tangential or Axial) and fixing type (clamp or jubilee clip).