Instrumentation cable buyers in Tennessee
For instrument engineers and stores supervisors holding signal cable, this page explains pairs, triads, shielding and why the tag carries the value.
Send us your reel list
Six details are enough for a first review: what the cable is, the metal, the size, the footage or reel count, the condition and where it sits. Photographs can follow by text or email. There is no fee and no obligation, and nothing moves until written terms are agreed.
Instrumentation cable carries the small signals between a sensor and a control system: 4 to 20 milliamp loops, thermocouples, resistance temperature detectors, and the discrete signals that go with them. It is 300 V cable in 16 and 18 AWG, built as twisted pairs or triads rather than as a simple bundle of conductors.
A reel of it weighs very little for its length, which is the first surprise for anyone used to power cable. That is also why the tag matters here more than the weight. The conductor count, the pair arrangement and the shield type are what make the cable suitable for a particular loop, and none of them can be guessed from a coil on a shelf.
With instrument cable the tag is the product; the copper is almost incidental.
Lot basics
- Voltage
- 300 V
- Sizes
- 16 and 18 AWG
- Construction
- Twisted pairs and triads
- Shielding
- Individual and overall
What a twisted pair or a triad is for
A pair is two insulated conductors twisted together, and the twist is what keeps electrical noise from coupling into the signal. A triad is three conductors twisted as a group, used where a sensor needs a third wire for compensation or excitation. A cable may contain one pair, several pairs, or a mixture of pairs and triads.
Each pair or triad may have its own foil wrap, with an overall shield or braid over the whole assembly. Individual shielding separates one loop from its neighbours inside the same cable; an overall shield protects the bundle from outside interference. Cable with both is common in plants where drives and high-current circuits share a tray.
- Twisted pairs and triads, not a flat bundle
- 16 and 18 AWG, 300 V rating
- Individual foil, overall shield or both
- Drain wires for terminating the shield
Chemical, paper and food plant stock
Chemical plants hold the widest variety, because a single unit may need thermocouple extension, RTD cable and shielded analog pairs in the same cabinet. Paper mills run long loops from the wet end to a control room and specify cable with good noise rejection. Food plants use it in washdown areas, where the jacket has to resist cleaning chemicals.
Those plants also hold spare reels, because instrument work is planned in advance and a shutdown is a bad time to discover a shortage. When a unit is revamped or a control system is replaced, the spare reels stay in the instrument shop and the new system may call for a different cable. That is where most of this material comes from.
Why the tag outweighs the weight
Copper content in instrument cable is small, so a recovery price is never going to be attractive. The value is in reuse, and reuse depends entirely on knowing what the cable is. A tag that names the pair count, the gauge, the shield arrangement and the temperature rating turns an anonymous coil into a product.
Without the tag we work from the jacket print, the pair count at a cut end and the shield construction. That is often enough for a common type. It is not enough for thermocouple extension cable, where the conductor alloy matters and the color code of the pair identifies the calibration, so those reels are worth photographing carefully.
Length still matters, but less than it does for power cable. A hundred feet of a specific shielded pair can finish a job that a thousand feet of the wrong type cannot start, so a short remnant with a clear tag is worth more than its weight suggests. The reverse is also true, and a long reel of an unidentified type is a hard sell.
Questions sellers ask
What is the difference between a pair and a triad?
A pair is two conductors twisted together, which is enough for a simple loop or a two-wire sensor. A triad is three conductors twisted as a group, used where the instrument needs a third connection, such as a resistance temperature detector or a compensated thermocouple circuit. The count is printed on the jacket and visible at a cut end.
Do you buy thermocouple extension cable?
Yes, and it is one of the few cases where the alloy matters more than the copper. Thermocouple extension cable is made from alloys matched to the thermocouple type, and the pair is color coded to identify it. Send a photograph of the tag and of the conductor colors, and we will confirm the type before quoting.
Why does the tag matter more than the weight here?
Because the copper in a reel of instrument cable is a small fraction of what the same length of power cable contains, so recovery value is minor. The cable is worth buying to reuse, and reuse requires knowing the pair count, gauge, shield type and rating. A clear tag supplies all four at once.
Can instrumentation cable be used for control circuits?
It can carry low-voltage control signals where the conductor size suits the load, though its 300 V rating and small gauge limit it. Most plants keep the two families separate for clarity in the trays. When we price a lot we treat instrument cable as signal cable, because that is where the demand sits.
Send us your reel list
Six details are enough for a first review: what the cable is, the metal, the size, the footage or reel count, the condition and where it sits. Photographs can follow by text or email. There is no fee and no obligation, and nothing moves until written terms are agreed.
Instrument cable in the shop?
Send a photograph of each tag, the pair or triad count, the shield type and the footage where it is known.
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