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| E-field probes for EMC immunity - cheap vs. expensive ? |
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| Jolle:
Thank you for your responses. I have been looking a bit more into the datasheets of the FP5000 and the TM-195 and there is no doubt that the 480836/TM-195 is less accurate. It also seems that the 480836/TM-195 are not properly calibrated since it is possible to enter a calibration factor (which it then uses throughout the entire frequency range...). From these information I guess the price comes down to the accuracy of the instruments, like buying a 0.1% voltage reference vs a 0.001%. For my application I do not need ±1dB accuracy and a FP5000 or similar therefore seems like overkill to me. But the cheap alternatives I have been looking at might also be a bit too cheap. Does anybody have any experience with any RF E-field strength meter they would recommend ? |
| Feynman:
Many TEM cell fabricators offer spread sheets where they show field strength dependent on the RF power (dbm) fed to the cell. Measuring RF Power might be cheaper than measuring V/m (in the case your RF source doesn't tell you already the RF power). And often times the fabricators give you hints in which areas of the cell to expect a reasonably uniform field. |
| Xandinator:
Maybe the cheapskate solution we employ is something that works for you as well: Use some (inexpensive) EMC field probes to characterize homogeneity and use the theoretical value as reference for the center (if you supervise students that also constitutes a nice task for them :D). Better than ±5 %. |
| ExaLab:
I use the Tenmars TM-195. Using the typical CAL factor of the unit, its accuracy above 1.9GHz is +/-1dB (plus the isotropic deviation) For those interested, I have the graph/table of the calibration factor vs frequency (not easily available ...) |
| ExaLab:
Below, the Calibration table and related graph for the TM-195. Please take into account its limited accuracy at low frequencies of the operating range. |
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