Which magnetic field sensor should I use?

In 2015, Spicer Consulting released two new magnetic field cancelling systems – the SC24 and SC26 which replaced the SC20 and SC20Fast. At the same time we changed our range of sensors. We renamed some to go with the new cancelling systems. We also created some new types of sensor. This article explains our thinking behind the sensor changes.

SC24/AC (Green). This new AC sensor replaces the SC20/AC sensor. It has a lower bandwidth of 25 Hz. It is designed for cancelling 50/60Hz AC power frequency fields and harmonics. It is also suitable for use with a TEM or dual beam instrument that puts out large steps in magnetic field when changing magnification or operating mode. The large field change temporarily overloads the AC sensor, but the 25 Hz lower bandwidth means that it automatically recovers very quickly.

SC24/DC+AC (Black). This sensor has bandwidth DC – 10 kHz so that it can be used to cancel slowly varying fields below 25Hz as well as 50/60 AC power frequency fields and harmonics. There is no need to use it in conjunction with an AC sensor for this purpose. This is actually the same sensor that we called SC20/DCMR – but we renamed it to indicate that it works with the SC24 and can cancel AC as well as DC fields.

SC26/AC (Blue). This fast AC sensor has a lower bandwidth of 25 Hz and sufficient upper bandwidth to cancel the 9 kHz fields that come from overhead wafer transports in semiconductor cleanrooms. It is the same as the SC20Fast/AC sensor and is now only for use with the SC26 cancelling system. (Previously we supplied this sensor for SC22 systems that were used with TEMs because they recovered faster from overload than the SC20/AC sensors. The new SC24/AC sensor recovers just as quickly, so we do not need to use the SC26/AC sensor for this purpose.)

SC11/Basic (Grey). This AC sensor is not compatible with cancelling systems. It has a lower bandwidth of 1Hz and an upper bandwidth of 20 kHz. It has double the dynamic range of the cancelling system sensors. It has built-in inputs for an accelerometer and sound level meter. It used with the SC11 software to make magnetic field measurements in microscope environments. The system using this sensor is very portable and excellent for measuring AC fields, including 9 kHz. With software filters, it can detect the presence of slowly varying fields down to 0.1 Hz, but cannot measure them accurately.

SC11/AC (Red). This new sensor is for use with the SC11/SI and is not for use with cancelling systems. It has the same magnetic field bandwidth and range as the SC11/Basic sensor, but no built-in inputs. It gives the SC11/SI the same AC field measuring capabilities as the SC11/Basic. We no longer recommend any other AC sensor for use with the SC11/SI.

SC20/AC (Grey). This sensor has been withdrawn and replaced by the SC24/AC. It had a lower bandwidth of 5 Hz, which meant that it recovered slowly from overload. There are relatively few situations where fields between 5 Hz and 25 Hz need to be cancelled and these can be covered by the SC24/DC+AC sensor.

The following table lists the currently supported sensor options

1 The SC24 works with AC sensors, but the lower cost SC22 is usually recommended when there is no DC field problem.

The following table lists the currently supported sensor options

1 The SC11/SI works with any combination of AC and DC sensors, but the above are preferred.
2 The SC11/AC sensor requires SC11 5.5 or later software.
3 The MEDA uMAG-01N works with the SC11/SI, but the SC24/DC+AC is usually preferred.