GM08 Gaussmeter

The GM08 is a hand-held, battery powered Gaussmeter that is operated via a simple menu and is supplied with a thin semi-flexible transverse Hall probe suitable for all but the very smallest applications. With a simple to understand display even non technical users will be capable of using the instrument. A graphical LCD display enables the reading to be displayed in a form that is easily readable, as well as display other data/settings on the screen at once.

The GM08 Gaussmeter has been designed and manufactured by Hirst Magnetic Instruments Ltd. A company with more than 50 years experience in magnetic measurement. This experience together with our extensive knowledge of the magnetics market has enabled us to design an instrument incorporating all the measurement functions a user is likely to need.

Functions

An easy to use menu enables you to change settings which are automatically stored when you switch off. On switch on it automatically remembers its previous setting. The range functions are directly accessible from a key on the keyboard to enable quick change between the 4 measurement ranges and auto range.

Measurement functions

The GM08 has a number of measuring modes that are ideal for a variety of different magnetic measurement problems. As well as standard DC mode the unit also supports peak detection with a bandwidth of 10kHz and AC modes that can show the RMS or the peak of the RMS of AC magnetic fields.

The measuring modes are all accessed via the menu on the instrument and the currently selected mode is indicated on the display at all times. The available modes are:-

• DC DC Magnetic field measurement
• DC PEAK Maximum positive peak reading of the DC field
• AC RMS True RMS (Root mean Square) of input signal
• AC MAX RMS Maximum true RMS (Root mean Square)
• AC PEAK Maximum positive peak reading of the AC field

Measurement ranges

The GM08 Gaussmeter has 4 measurement ranges to cover a wide range of measurement applications:-

• 0 - 2.999 T - resolution 1 mT
• 0 - 299.9 mT - resolution 100uT
• 0 - 29.9 mT - resolution 10uT
• 0 - 2.999 mT - resolution 1uT

1 mT = 10 Gauss = 0.796 kA/m (in free air)

The GM08 also has an auto-range option where the meter will automatically change range to maximise resolution.

Measurement units

The GM08 can measure in Tesla, Amps/m, Gauss or Oersted. The units are selectable by the user using the menu. Any data saved with the capture system can be automatically converted between measurement units and will display in the currently selected units when the data is recalled.

The currently selected units are displayed on the main screen at all times.

Data capture and hold

The GM08 also has the ability to hold the current measurement. When the GM08 is in HOLD mode the button on the probe will freeze the current reading, ideal for measuring in a difficult spot or to ensure the reading is recorded correctly.

The GM08 also has the ability to store in non volatile memory up to 100 samples with date and time information. The GM08 incorporates a real time clock for accurate simple date and time logging. When the GM08 is in STORE mode, pressing the probe button will cause the GM08 to log the current reading to its memory.

These values can later be RECALLED, either on the Gaussmeter using the menu or via PC software when using the RS232 or USB communications link. Data is shown on the Gaussmeter and uploaded to the PC complete with date and time. When uploading to the PC the units used, the range used and the data and time are transmitted for additional information.

Power down

The GM08 has a number of utilities options allowing the operator to disable or select various options and utilities within the instrument. The GM08 features an automatic power down timer to save batteries, if the unit is left on. The time duration of the power down can be set in the utilities menu. It is also possible to disable the power down completely from the menu.

Nulling and zero

The GM08 features two zeroing modes. Auto-zero and Null. Auto-zero performs an internal calibration and checks the zero offset of all ranges and modes. This function should be performed at frequent intervals to ensure accurate readings are taken. A zero gauss can is supplied to shield the Hall probe from the Earth's magnetic field which will induce a small offset if the probe is not shielded.

The Null function can be used to "Null" the current field, much in the same way a "tare" operation is utilised on weighing scales. The current reading is taken as an offset and set to zero and all subsequent readings will have the same offset applied. This is ideal for relative measurements.

Multilingual

The GM08 has a facility to operate its menu structure in: English, French, Spanish, Italian, German and Portuguese. The languages can be selected from the menu at any time. What ever language is selected is remembered at the next power on.

Display

The GM08 features a graphical LCD display that enables the main measurement reading to be displayed at an easy to read size and also allow the display of all the current operating modes and units. The display also allows the simultaneous display of the menu system at the reading when making changes to the mode or options of the Gaussmeter.

Calibration

The GM08 is calibrated to standards traceable to the National Physical Laboratories (London UK). During manufacture, the accuracy of Nuclear Magnetic Resonance (NMR) is used to determine the irregularities and non conformities of the GM08 and its Hall probe. This is stored and used mathematically to automatically correct readings taken by the GM08. A static field is applied to the Hall probe and this field is measured using the NMR probe (whose absolute accuracy and uncertainty is known and traceable to NPL standards). The difference between the GM08's reading and the known reading is used to calibrate the instrument and ensures the instruments accuracy is better that 1%.

Software

The GM08 is supplied with full software to enable the direct use of the instrument on a PC running Microsoft Windows. Various utilities and example files (including source code) are also provided to enable integration of the GM08 into existing systems. The various examples include C command line tools. Visual Basic graphical tools and embedding the measurements into Microsoft Excel.

A shared library is provided (.dll /.so) that wraps all the function calls to the instrument and exposes a simple to use application programming interface (API). The shared library will also compile and operate on various Unix based operating systems including Linux.

Applications

The GM08, GM07 and VGM02 are ideal for inspection and measurement of magnetic flux density of magnets and magnetic assemblies in both goods inward and Quality Assurance environments. Where individual measurements need to be recorded the GM08 will store and upload not only the measured values, polarity, measurement units and measurement function, but also the time at which the measurement was taken.

Applications include:

• Computer disk drive actuators
• Loudspeaker air gaps
• Electric motor air gaps
• Transformer stray field measurements
• Bending magnets
• Non destructive testing (magnetic)
• Goods inward and quality assurance inspection
• Automated magnet calibration

Probes

The GM08 is supplied with transverse Hall probe (TP002) as standard. The probe is fitted with a push button enabling the operator to HOLD and STORE measurements and orientate the probe for polarity readings. All transverse and axial probes are fully interchangeable with Hirst Magnetic Instruments Ltd's GM04, GM05, VGM01, VGM02, GM07 and GM08 Gaussmeters. Custom axial and transverse probes are also available. Please contact the sales office for more information.