Information Library
Measurement Knowledge <Part 6 >
1. Troubles with hum
Since their output is so faint, load cells require adequate noise countermeasures such as quality shielded cables or protective tubing. In most cases, the strongest source of noise in the environment around load cells and weighing gauges is power frequency noise, which is generally 50 or 60 Hz. This is known as hum noise.
However, A&D’s weighing indicators have excellent noise elimination properties against this power frequency and are not very affected by it. Strangely, this can be a problem as there are even customers who do not feel the need to use shielded load cell cabling. (Of course, we do not recommend this.)
However, power frequency is not limited to 50 and 60 Hz. The closest one is an inverter. Inverters control the speed of a motor by changing the power frequency, and this generates frequencies other than 50 and 60 Hz. Furthermore, inverters generate various frequencies and voltages through on/off switching at very short intervals when switching between direct current and alternating current, and this switching frequency also generates noise. Therefore, various frequencies, along with strong noise, are often generated in environments in which inverters are used. As mentioned above, the most basic way to counter this noise is through shielded wiring and piping. However, our products that use the High Performance Digital Filter are designed to resist not only sources of vibration such as the floor but also the various frequency noises generated by inverters. We recommend these products to customers worried about noisy environments.
