What happens if I apply AC or DC field over the range of my sensor?

If it is saturated by an AC field, then it is not too much of an issue. If you can reduce the amplitude of the field progressively to come out of saturation (similar to what would be done during deperming) or stop the AC field when it is close to 0. If it is saturated at DC, or you switch off abruptly an AC field at high amplitude, then refer to the overload hysteresis figure in the brochure. Typically an offset will be added, the more important the offset for the higher the over-range.

Is the sensor’s output affected by the voltage supply?

There is always some overshoot above the full-scale output. Typically, the output of the sensor is driven by the op-amp on the electronics which will have an output function of the voltage supply. If you supply 12V, for instance, you may have a maximum output which will be around 10.5V. As you increase the voltage supply you can gain a few hundred mV on the output (we no longer guarantee that the output will be linear). So if you end up with field above 110-120uT, the output will reach the rail, which will be slightly above 10V, and stay there until the field comes back within sensor range.

How long can the cable to my sensor be?

We can drive sensors with cables up to a several hundred metres, but this depends on the sensor being used. Contact sales@bartington.com for more about using cables over 30 metres long.

What signal does the voltage output from the magnetometer/PSU1 represent?

The output voltage of ±10V or ±3V (full scale output dependent on sensor, please refer to individual brochures) represents the full scale range of your sensor. For example, if you have a ±100µT range sensor on a ±10V full scale output the scaling will be 100mV/µT. This voltage gives both the DC and AC components of the field.

What is the resolution of a magnetometer?

As the sensors have an analogue voltage output, there is no defined resolution.  Instead, the smallest fields detectable by a sensor are dependent mainly on the sensitivity of the voltmeter being used to read the output voltage, the internal noise of the sensor, and environmental noise. The internal noise of the sensor is the absolute minimum that the sensor can detect. However, the magnetic noise in the environment is higher than this, and will limit the smallest variation that can be detected. If data processing is performed, the environmental noise can be removed and the sensor noise level can be reached. The scaling (sensitivity of voltmeter) of the analogue output varies with the range of the sensor. Scaling values for different sensors are listed in the sensor’s datasheet. The scaling value increases as the range of the sensor decreases, increasing the sensitivity as the range is reduced.

Can I mount a Mag-03MC to a surveyor’s tripod, using the wooden bracket and nylon screws?

We are unaware of anyone who has a design that you can use. However, Bartington manufactures the Mag-03-MC Mounting Bracket DR0746 for similar applications. For a drawing of the bracket, see figure 17 in the Mag-03 Operation Manual. This product could be adapted for your application. It is very important to ensure that there is no steel in the tripod. We supply an aluminium tripod for mounting the Mag03MC, the Mag-T. This extends to 1.3 metres, and comes with a tripod adaptor for mounting the Mag-03MC. Contact us for further details.

Can I use the sensor at high temperature?

The Mag610/611 and Mag614-FL have been tested to operation above 175°C. This relates to the probe only. To learn more see High temperature Magnetometers.

Can I subject the sensor to shock and vibrations?

We offer aerospace and high temperature downhole sensors have been formally subjected to shock and vibrations tests. Where applicable, the test method is provided in the product brochure. Other sensors are used in these environments successfully. For example Mag-03 are regularly mounted onto aircraft. To learn more see Aerospace.

How far from the electronics can I position the sensor head in a two part sensor?

Most two part sensors have a maximum separation of ~5m. This depends on the sensor being used, to refer to the product datasheet for details.

How close together can I place two sensors?

If one sensor is active and the second one off, the sensors should be kept about 4-5cm apart (sensor dependent as the dimensions of the core material vary). The interference between two sensors as described above is a small DC offset on the active sensor. When the two sensors are powered (unless you are using multiple Mag612 or Mag619 with the excitation synchronised), the minimum distance should be between 15-20mm. A beating phenomenon may otherwise occur where one sensor is picking up the excitation from the other. As it is unlikely that the excitation will be at the same frequency and in phase, a beating (low frequency signal) appears on the output of the sensors.

Are flying leads/cable connecting sensor to electronics shielded?

No, these are not shielded, and can therefore be the source of noise pick-up in the system. It is therefore essential to shield these to prevent any issues.

What is the breakthrough?

This is the amount of signal at the excitation frequency of the sensor present on the sensor’s output. See also Glossary.

Can I use a sensor in vacuum?

Some sensors are designed for operation in vacuum (Mag-03IEHV for example – tested to pressure of 1e-4 Pa). Customers have in the past used non-tested sensors in low pressure environment, but we do not guarantee that the sensor will not be subjected to damage or severely outgas.

Can I use the sensor at low temperature?

CryoMag sensors provide high precision measurements of static and alternating magnetic fields at temperatures down to 2K. They are available with standard 3-axis probe, or 3 single-axis sensor heads. To learn more see CryoMag. The Mag F and G probes are rated for cryogenic use. Sensors with integrated electronics will not operate at low temperature. Two-part sensors will suffer mechanical damage at low temperature, such as wire insulation breaking. To learn more see the Mag-01H product page at bartington.com.

How do I know which noise version my sensor is?

The noise is indicated by the letter found after the product/package reference. L is for low noise, no letter will indicate a standard noise and B a basic noise. See the product datasheet for the noise levels.

Where are the fluxgate sensors located?

Where possible, the fluxgate sensors are located in the centre axis of the sensor below the axes marking on the sensor. However, this is for indication only (and not always feasible to position the label right above the axes). For exact position, refer to the sensor’s outline drawing available on the product page at bartington.com.

Which is the sensor’s mounting face?

Refer to the sensor’s outline drawing available on the product page at bartington.com as the mounting face change from sensor to sensor.

What is the measuring range of a sensor?

The range is included at the end of the sensor name. For example, a Mag-03MC70 is a Mag-03 with measuring range of 70µT. The range is also printed on the sensor’s label.

The CU1 is emitting a loud continuous noise

This noise indicates that the connection between the CU1 and the National Instruments (NI)/PC/Software has not been detected. To troubleshoot this please shut everything down, then try restarting everything in the following order: your PC + Software, then NI card, then CU1 and finally the PA1.

How does the orthogonality error effect my measurement?

The orthogonality error is a constant error. It is due to the three axes not being exactly 90 degrees from each other. A correctional matrix can be applied to get the readings that would be expected if the axes were perfectly orthogonal to each other.

Can I measure the absolute magnetic field accurately or only variations in magnetic field?

In order to achieve absolute measurements, scaling, orthogonality and offsets errors will need to be corrected. Multiple papers discuss the calibration of fluxgate magnetometers for use in total field measurements with varying level of success. One example is: Munschy et al., 2007. Magnetic mapping for the detection and characterization of UXO: Use of multi-sensor fluxgate 3-axis magnetometers and methods of interpretation: Journal of Applied Geophysics, number 61.

Is the magnetometer output signal conditioned?

The output from the magnetometer is an analogue voltage which can be connected to the customers own appropriate data acquisition system(DAQ). It should be noted that there is some residual breakthrough from the sensors excitation which is partially filtered inside the sensor (by an analogue low-pass filter). This is then further filtered out by our power supplies and DAQs. If using own acquisition system, you would need to filter this out either by fitting an analogue low pass filter or by digitally sampling at least double the excitation frequency of the sensor. Alternatively, we could provide a PSU1 which would deliver power to the sensor and filter the output so that you can then connect it to your own DAQ without the need for additional filtering.

Why am I seeing lots of aliased noise in my data?

Does your acquisition system setup include one of our power supply or data acquisition units? If not make sure you have applied a suitable low pass filter in your setup to deal with the excitation frequency of the sensor. You can either apply an analogue low pass filter, or digitise the signal at a frequency at least twice that of the excitation frequency. See your sensor’s datasheet for details on excitation frequency and breakthrough levels.

I am applying a known DC field and I am not reading the correct value in the measurements tab in the software

Please check in the software settings that the measurements are set to DC and not RMS or pk-pk in the measure tab.

No power is being provided to the sensor plugged into the DUT port of the CU1

Make sure to check that the DUT PSU is enabled in the software and that a suitable voltage has been set. See the sensor datasheet for the correct voltage range.

The Grad-601 works for other people but not for me. A Coarse error appears during setup of the equipment?

It is important that the user is magnetically clean. Make sure to remove all metallic items from your person: watches, mobile phones, jewellery etc. The steel underwire in bras and parts of shoes will also contribute and are often forgotten. Those with metallic implants such as plates, pins or pacemakers may be unable to use the equipment. To test your magnetic cleanliness set the gradiometer to the 100nT range with the appropriate setting for the number of sensors and run in Scan mode. Hold the gradiometer stationary and check the readings when the operator approaches the gradiometer sensor. The operator should check all parts against the end of a gradiometer sensor until a change of less than 0.1nT is seen.

Is the MS2 range limited by the 4 digit display?

Indeed, there is a limitation to 4 digits on the display, however, there is a workaround available for samples above this range. Described for MS2B but will also work for other sensors, where the sample is brought closer to the sensor slowly. Place the sample on the platen and lower it slowly within the sample cavity while continuously monitoring the display readings. You will notice that as you lower the sample the susceptibility value increases up to 9999 and then switches back to 0000. That practically means that your sample has a value over 10000 of which the first digit is omitted so you only see 0000. Keep lowering the sample until you reach the centre point and note how many time your values resets to 0000. i.e. for a value of 35000 the display will reach 9999 three times during lowering and display 5000 once the platen has been fully lowered to the centre point.

What is the recommended time period for measurements?

It depends on how stable the sample and the temperature are. In the lab, where MS2B an MS2C are most likely to be used and conditions are more stable, 5 sec measurement period is fine whereas in the field where MS2E and MS2K are used, 1 sec measurement is recommended.

MS2 Meter not communicating – using USB serial Adaptor.

Ensure that the drivers for the USB / serial adaptor are up to date and that the coms settings as matching that of the MS2. For USB/serial adaptor updated drivers: http://www.ifamilysoftware.com/news37.html

When should a sensor be calibrated?

We recommend that sensors are calibrated every 2 years. Sensors must be returned to Bartington Instruments for calibration. To learn more, see Product Calibration Service.