3D-magnetic field probes AS-U3D GEO-X for ±200 µt

Transcription

1 3D-magnetic field probes AS-U3D GEO-X for ±200 µt measurement of X, Y, Z or Σ DC and AC field measurement measurement range: ±200 µt (2 G) high bandwidth: DC 500 Hz linearity error: <0,8% ±0,2 µt compact probe: 66 x 66 x 66 mm³ Thread for photo tripod analog output factory calibration certificate with traceability Made in Germany The probe AS-U3D GEO-X is a 3-axis measuring system with which the magnetic field can be measured independently of the orientation of the probes. With its maximum measuring range of ± 200 µt, it is particularly suitable for measuring very small magnetic fields such as the Earth's magnetic field. The probe AS-U3D GEO-X is compatible with the other probes from our program of AS-active probes. Thus, it can also be used with all devices that are intended for the connection of an AS active probe. The probes can be used together with the Teslameter FM 302, the AS-Probe adapter and the AS-Adapter 3. The AS active probes are active measuring probes for measuring the magnetic induction. Our AS probes have active electronics so that a calibrated analogue signal is available at the plug. These are high-quality transducers for the measurement of DC fields and alternating fields. Version from Seite 1 von 13

2 The 3-axis probe AS-U3D GEO-X contains in its probe housing 3 sensors for measuring the three spatial directions of the magnetic flux density. With dimensions of only 66 x 66 x 66 mm³, the housing is very compact and therefore also suitable for measuring in confined spaces. The probe housing has a threaded insert with the standard tripod thread (1/4 20 UNC). This allows the probe to be mounted on almost any tripod if required. It is also possible to mount one of the commercially offered handles on the probe. The tripod / handle should be made of non-magnetic material. The scope of delivery already includes a mini tripod with telescopic legs (maximum height 155 mm). An electronics housing is integrated in the probe cable just before the probe plug. This houses the active electronics of the probe. The electronics housing is designed so that it can be mounted under a Teslameter FM 205 or Teslameter FM 302 for measurements. Fittings on the electronics housing engage in the recesses on the bottom of the Tesla meter and ensure that the two devices fit snugly together. Velcro straps are used for fastening. These are drawn through two channels in the electronics housing and placed around the attached teslameter. The Velcro straps are included. Version from Seite 2 von 13

3 With a switch on the electronics housing different measurement modes can be selected. In each case, the signal of one of the individual axes (X, Y, Z) or the total signal (Σ) formed from the individual axes can be forwarded to the connected Teslameter FM 302. In the case of the total signal, one can again choose between the DC or DC component (ΣDC) and the AC component or alternating component (ΣAC). In single-axis measurement, the probe behaves like a normal uniaxial probe. The full bandwidth of the probe is available. With the Teslameter FM 302, both the DC component of the field (FM DC mode) and the RMS value of the AC component (FM AC mode) can be determined. In the ΣDC mode, the absolute value of the total field is determined from the three individual directions and this signal is sent to the connected Tesla meter FM 302. This mode is for measuring the DC component. The bandwidth is 2 Hz. The FM 302 is operated in DC mode. In ΣAC mode, only the alternating part of the total field is determined. The bandwidth of the measurement here is 5 Hz to 500 Hz. A DC signal is generated whose level corresponds to the effective value (RMS) of the total alternating field. This signal is sent to the connected Teslameter FM 302. Therefore, the FM 302 must also be operated in the ΣAC mode in DC mode. Version from Seite 3 von 13

4 Functional Principle Most available magnetic field probes are single axis probes. That means that they can only detect fields in parallel to their particular measurement direction. If the AS-probe is positioned with an angular to the field, the displayed value is lower than the actual field. The display value results from the following relation. cos To avoid this problem the AS-U3D GEO-X are designed as 3D probes. There are three sensors mounted in the probe head which are aligned perpendicular to each other. These three sensors measure the three axis of the magnetic flux density. From the signals of the single axis the absolute value of the total signal can be calculated. The calculation is carried out according to the following formula This principle works for all orientations between probe and magnetic field. Required is the perpendicularity of the single sensors. In the probes AS-U3D GEO-X this calculation is implemented by an efficient technology. Thus even fast signals from 0 Hz to 500Hz can be processed without problems. Sign and Directional Information It will always be calculated just the magnitude of the field. Furthermore it can be seen from the formula, that the value of the total field is always positive. The absolute value arises from the squaring of the three single signals. The information about the direction of the magnetic field is not kept by the calculation of the total field. Therefore the measured value of the total field is always positive. Version from Seite 4 von 13

5 Constant Field Measurement with Overlaying Alternating Fields The squaring of the values causes a rectifier effect. This rectification especially affects the measurement of alternating fields. Their rectified signal generates an additional constant component in the measurement signal. This problem is caused by the principle of measurement and affects all measurement systems which derive the total signal from the single axis. It is essentially to observe the consequences at all 3-axis measurements. At 3-axis measurements overlaying alternating fields generate an error in the measurement of constant fields. Therefore the presence of alternating fields should always be checked before doing constant field measurements. For constant field measurement the probes AS-U3D GEO-X include additional low-pass filters with a cut-off frequency of 2 Hz. These will be activated automatically in the measurement mode ΣDC. These filters attenuate the influence of alternating fields to the measurement. However, a total suppression of the alternating components is not possible. Especially the influence of low frequency alternating components is reduced but still existing. Due to the low-pass filters, the suppression for alternating fields with frequencies of 16.7 Hz or higher is at least 60 db. The measurement error in DC field measurement is thus less than -60 db times the ratio of AC field amplitude to DC field amplitude. For usual fields occurring in the technical field, such as 50 Hz (mains frequency, transformers) or even 16.7 Hz (traction current), the influence is only very minimal. Influence of the Low-Pass Filters to Rotation of the Probe in Constant Field The low-pass filters affect also changes of the signals which arise from the rotation of the probe. Indeed the total field remains unchanged but the components of the field measured by the three sensors change. Here the necessary low bandwidth of the filters prevents a fast reaction to the change of the measurement signals. During fast rotation of the probe temporary a deviating measured value is displayed due to the integrated filters. Therefore the probe should be turned only slow to allow the filters to follow the measurement signal. Measurement of Alternating Fields At the measurement of alternating fields in position ΣAC the constant component of every sensor axis is separated by a high-pass filter. The cut-off frequency of these filters is 5 Hz. Afterwards the calculation of the total field is performed. Thus only the alternating components contribute to the measurement result. Here the rectifying effect of the total field calculation has to be observed, too. To gather the effective value of the signal the processing has to be done from DC on. As the Teslameter FM 302 in alternating field measurement measures only above a low cut-off frequency of 5 Hz the signal cannot be evaluated directly by the Teslameter FM 302. Therefore the electronic of the probes AS-U3D GEO-X contains an additional RMS converter for alternating field measurement. In addition see also the chapter Fehler! Verweisquelle konnte nicht gefunden werden. at page Fehler! Textmarke nicht definiert.. This module carries out the correct effective value generation. It generates a voltage signal proportional to the effective value. Therefore the FM 302 has to be operated in measurement mode DC even in mode ΣAC to achieve a correct display. Version from Seite 5 von 13

6 Influence of the High-Pass Filters to Rotation of the Probe in Constant Field The high-pass filters in the probes AS-U3D GEO-X are intentionally designed with a very low cut-off frequency of 5 Hz. This allows even the measurement of very low alternating fields. But if the probe is rotated in an overlaying constant field (e.g. the earth magnetic field) during alternating field measurement a changing measurement signal appears at the sensors. During faster rotation of the probe these changes cannot be suppressed completely by the high-pass filter. During fast rotation of the probe temporary a deviating measured value is displayed due to the integrated filters. Therefore the probe should be turned only slow to allow the filters to follow the measurement signal. Oversteer The sensors used have a limited measuring range. Signals greater than ± 200 µt lead to overloading of the individual sensors. The filters used are located after the sensors. Therefore, the entire field of alternating field and constant field is always to be considered. DC field and superimposed alternating field must not overdrive the sensors. This would lead to deviating measured values. Damage to the sensors does not occur due to overload. Only the hysteresis can lead to a shift in the offset of the individual axes, in particular in the case of strong DC fields. In case of doubt, e.g. for complex alternating fields, the signal should be checked with an oscilloscope at the analog output of the Teslameter FM 302. Functional diagram The following diagram once again shows the functional diagram of the probe with the three sensors, the lowpass and high-pass filters, the total field calculation and the rms value evaluation for alternating field. The switching of the filters takes place automatically according to the selected measuring mode. To save energy, the block for total field calculation is only activated if the total field is also to be measured. In single axle measurements, this block is deactivated. The same applies to the RMS converter. This is only active in the ΣAC measurement mode, but deactivated in all other measurement types. Version from Seite 6 von 13

7 Measuring direction and polarity If one of the individual axes is selected as the measuring mode, the AS-U3D GEO-X behaves like a normal uniaxial probe. If the AS probe is positioned at an angle to the field during uniaxial measurement, the displayed value is lower than the actual field. In uniaxial measurement, the direction of the field is also indicated by the sign of the measured value. The direction for a positive display value is indicated by the arrows of the axes on the probe housing. In the case of the three-axis measurement, the amount of the total field resulting from the three individual directions is determined. The measured value is ideally independent of the angle between the probe and the magnetic field. For three-axis measurement, only the amount of the total field is displayed. Direction information is not output. Therefore, the displayed reading is always positive. See also the information on the principle of operation of the probe on page 4. Version from Seite 7 von 13

8 Sensitivity overview The AS-U3D GEO-X 3-axis AS active probe supplies a calibrated, analogue output signal whose level depends on the measured field. Table 1 shows the measuring range and the transmission factor of the probe. Class Area probe without Teslameter transcription factor probe Ultralow: 200 µt 2 G 159,2 A/m 2 V / 200 µt Table 1 The Teslameter FM 302 has the option of switching the amplification levels x1, x10 and x100. This makes it possible to cover a wide measuring range with each probe. In addition, the Teslameter FM 302 offers a switching of the display unit. Table 2 shows the resulting ranges and the transmission factors for the analog output. Class Ultralow: Areas and transcription factor with Teslameter FM 302 (FM 205) area x1, x10, x100 x1 x10 x µt 20 µt 2 µt 2000 mg 200 mg 20 mg 2000 m Oe 200 m Oe 20 m Oe 159,2 A/m 15,92 A/m 1,592 A/m 2 V / 200 µt 2 V / 20 µt 2 V / 2 µt Table 2 Units T Tesla G Gauss Oe Oersted A/m Ampere pro meter For conversion of the magnetic units see our application note PE005 Magnetische Maßeinheiten und deren Umrechnung. Version from Seite 8 von 13

9 Technical data measurable flux density max. ±200 µt or 140 µt rms areas (with FM 302) ±2 µt; ±20 µt; ±200 µt measurement settings 5 various; via selector switch X: single signal X-axis Y: single signal Y-axis Z: single signal Z-axis ΣDC: sum signal DC (average) ΣAC: sum signal AC (rms value) sensor volume 3 sensors in 33 x 33 x 33 mm³ effective sensor volume Ø 6 mm x 25 mm ever axis squareness of sensors ±2 transfer factor 1 V / 100 µt bandwidth (-3 db) single axis: DC 500 Hz ΣDC: DC 2 Hz ΣAC: 5 Hz 500 Hz rise time (X, Y, Z) <0.3 ms rise time (ΣAC) typ. 0.3 s linearity error (X, Y, Z) temperature coefficient (X, Y, Z) zero point drift (X, Y, Z) hysteresis (X, Y, Z) noise (X, Y, Z) <0.8 % ±0.2 µt (to 25 C) max. 0.1 %/K (10 C to 50 C) max. 10 nt/k (DC) max. 0.1 % from measurement typ. 4.5 nt RMS (10 Hz 1 khz) typ. 6 nt PP (DC 10 Hz, 50 s) error of vector formation max. 0.2 % ±0.3 µt validity of vector formation for fields 0.2 µt probe housing tripod thread cable length electronic housing 66 mm x 66 mm x 66 mm without cable 1/4-20 UNC (thread) 2.5 m 110 mm x 75 mm x 25 mm working temperature range +5 C to +50 C storage temperature range -10 C to +60 C max. relative humidity 70 % by +35 C Version from Seite 9 von 13

10 supply ±3 V through FM 302, AS-probe adapter or AS-Adapter 3 +6 V through PLC connecting plug 15 pol. SubD internal resistance <1 Ω typ. linearity curve from single axis 2,5 2 1,5 1 B [ µt ] 0,8 % ±0,2 µt 0,5 B [ µt ] , ,5-2 -2,5 Use of the probe AS-U3D GEO-X with Teslameter FM 302: Normally, the plug of the probe electronics is simply plugged into the tesla meter and the electronics housing is fixed to the Teslameter FM 302 with Velcro straps. It can be started immediately with the measuring. The desired measuring mode can be set via the switch on the electronics housing. All other options of the Teslameter FM 302 such as the calibrated analogue output, the control via USB or the power supply unit can be used as well. Further details can be found in the data sheet of the Teslameter FM 302. Version from Seite 10 von 13

11 Use of the probe AS-U3D GEO-X with AS-probe adapter: The AS-probe adapter amplifies the analogue output signal of the probes to ± 10 V, which corresponds to the typical range of analogue PLC inputs. To be universally applicable, the AS-Probe adapter has a wide input voltage range of 9 V to 36 V and provides the ± 3 V required to supply the AS active probes with high accuracy. In addition, the measuring signal is galvanically isolated from the supply voltage. The following figure shows an example application of a probe AS-U3D GEO-X with an AS probe adapter. Further details can be found in the data sheet of the AS-probe adapter. Version from Seite 11 von 13

12 Further variant: AS-U3D GEO-X x + y + z syn-out with AS-Adapter 3:: Three AS probes can be operated simultaneously on the AS-Adapter 3. The AS-Adapter 3 supplies all connected probes. The analog output signals of all connected AS active probes are available simultaneously, in parallel and at full frequency at the BNC connections "OUT X, OUT Y, OUT Z" for e.g. an oscilloscope and at the terminal contacts "OUT X-Y-Z" for a PLC system. The AS-Adapter 3 has table feet and a DIN rail mount for control cabinet mounting. The following picture shows an example application The probe AS-U3D GEO-X x + y + z syn-out is a measuring system with three sensors arranged at right angles. The signals of these three sensors are output in parallel. This allows the three axes of the magnetic field to be measured simultaneously and independently of each other. For each of the three single-axis signals, the probes have a separate 15-pin SubD connector. Version from Seite 12 von 13

13 Included in Delivery: AS- active probe AS-U3D GEO-X Velcro straps for mounting the electronics housing under one Teslameter FM 205 or Teslameter FM 302 mini tripod with telescopic legs (maximum height 155 mm) Instructions Factory calibration certificate with traceability Suitcase for AS- active probe AS-U3D GEO-X, Teslameter FM 302 and additional equipment Options: Probe extension cable 2 m, 5 m or 10 m without influencing the measurement result Application Notes On our website (/applikation.php) under Application you can find many additional documents with information, hints and examples for measuring of magnetic fields. Questions? Do you have any question about a measuring task? Call us, we would be pleased to advice you. As manufacturer of this system we can fulfill your desires about developing AS-active probes, changing of measurement range, changing of gain factors or other needs. Please call us or send us an . Gladly we accept your suggestions, your PE Team. Version from Seite 13 von 13