When it comes to measurements, noise can be a big problem. Accuracy is hugely important and electrical noise can influence temperature measurements enough that it can be hard to make a correct interpretation of thermocouple readings. Here are four types of noise that can create problems, plus tips on how to deal with them.
If a voltage source is coupled capacitively in an instrumentation circuit, you may have static noise issues. You can help solve this problem by placing the circuit in a total coverage shield. This will isolate the wires from outside influences while the grounded shield intercepts any static.
When currents flow through equipment, magnetic fields will radiate around the conductor. Unfortunately, this magnetic force can pass between conductors, resulting in a current that opposes the magnetic field and superimposes noise on the signal. To avoid this problem, twists the wires in the circuit. This will cancel the noise and get you back in business.
Too much talking can make it quite hard to listen. Cross talk occurs when multiple circuits are carried in the same conduit, leading to more noise in the circuit. Cables with individually-shielded, isolated pair shields can block noise from adjacent pairs, making it easier to get accurate readings.
Common mode noise can be cause by multiple grounds in an instrument circuit that cause a current to flow between the two of them. It can also happen in thermocouple extension cable circuits where the couple is connected electrically and physically to it as well. Grounding circuits at only the thermocouple can help remove noise, while receivers with a high common mode rejection ratio can help control interference.
QUALITY READINGS WITH QUALITY THERMOCOUPLES
Noise can be a major issue, but it’s even harder to get good readings with bad thermocouples. GeoCorp is a thermocouple manufacturer that works hard to take care of our customers, even going as far as maintaining a calibration laboratory to assure quality. Contact us today if you need good thermocouples that will help you ensure that measurements aren’t a problem.