Compensating cables are indispensable for precise temp. measurement at remote measurement points, they serve as extension leads from the thermocouple sensor to the measuring instrument. Compensating cables are made from metallic materials having similar thermoelectric properties as the thermocouple in use, the extension wires are made with similar material as of thermocouple element and are expensive, but cheap alloys of different combinations having milli-volts (e.m.f.) matched as closely as possible to the thermocouple at ambient temperatures to thermocouple are compensating wires. We supply insulation and sheathing to meet the various applications, there is a choice of PVC, Asbestos, Silicon, Fibre-glass, PTFE having screen of Stainless steel, Tinned plated, Copper wire or silver plated copper wire.

PVC Sheath

PVC insulation sheath has been widely used as a good substitute for rubber insulator. At YAMARI, PVC is used as an insulating material of standard compensating cables for general use.

Recommended Temperature Range: -20˜+90˚C

Glass Fiber Sheath

Glass fiber is known as a traditional high temperature insulation material because it has excellent incombustibility, heat resistance, electric insulation, and chemical stability. Although single glass fiber is not hygroscopic, bundled cover are somewhat hygroscopic. So, silicon or other resin is impregnated and baked over them to prevent moisture absorption.

Recommended Temperature Range: 0˜150˚C

Silicon Rubber Sheath

Silicon rubber has been widely used as an excellent insulation material with less deterioration physical properties even under hostile conditions. It has almost same electric properties as natural rubber and no serious change in voltage withstanding value occur over recommended temperature range. It has also good resistance to chemicals (except for concentrated Alkalis), oils and grease, outdoor and ozone environments. Recommended Temperature Range: -25˜+180˚C

Teflon* Cover

Teflon is the best insulation material among organic materials in respect of heat resistance, chemical Resistance, electrical insulation, high frequency resistance, weather resistance, etc. high mechanical strength and, especially, high pressure resistance over wider range of operating temperatures. Recommended Temperature Range: -25˜+200˚C. *Teflon is the registered trade mark by DuPont, U.S.A.

Metal Sheathed Compacted Mineral Insulation

The insulation material is fine grain MgO which is similar insulant to Metal Sheathed Thermocouples. Inorganic ceramic powder insulation tightly holds extension or compensating wires inside the Metal Sheath, composing perfectly integral construction. This M.I. Extension or Compensating cable can withstand fire or high temperature, corrosion and mechanical shock and is approved as the only non-inflammable safety cable. Available in all calibrations with various metal sheath such as Copper, Cupro-Nickel, Stainless Steels, etc.Cable Sizes 1.6 mm˜8.0 mm O.D. Temperature Range: 20˜270˚C but the cable withstands high temperatures up to 900˚C. Recommended for wiring at hazardous location without conduit tube.

Maximum Length of compensating cable

Many factors can affect the usable length of a thermocouple. As a guideline, under 100 feet with 20 AWG or thicker wire in an area free of electromagnetic interference usually is fine. Two of the main factors in determining useable thermocouple length are total loop resistance and preventing electrical noise getting into the signal. Because different thermocouple wires are made of different materials, the resistance will vary based on the type as well as the wire diameter and length. The input resistance of the amplifier circuit to which it is attached affects the allowable loop resistance. But as a guideline, typically the objective is to keep the total loop resistance under 100 ohms. Loop resistance is determined by multiplying the length in feet by the resistance per double feet (remember 1 foot length of run includes 1 foot from each of the two t/c wires) as shown in “Resistance Vs Wire Diameter” table for thermocouple type and gauge. Remember in your calculations to include the probe (when used/applicable) in addition to the wire length. The second major factor in running a thermocouple wire is to keep it away from any electromagnetic fields. Thermocouple wire creates a low voltage signal and should not be run near power wires, motors, etc. To help minimize noise pickup, a metal over braid or twisted shielded wire is commonly.used.

The insulation on thermocouple wire is color coded for identification. Common guidelines include that the negative lead in insulated thermocouple wire is red. The positive lead has the color of the thermocouple as well as the overall color of insulated extension grade wire. The outer jacket of thermocouple grade wire is typically brown. For high temperature wire, it is common to have a color coded tracer thread in the white material. For information on usable temperature ranges for the insulation see the “Wire Insulation Identification” table below.