I have access to various types of equipment I used to test this meter. The ED88Tplus from Cornet accurately reads RF (radio frequency) strength from ~1.5G Hz to ~ 2.5 GHz, and it reads somewhat low outside that frequency range. At a lower frequency of 300 MHz, it reads ~90% low, and it also reads ~90% low at ~ 5 GHz. That is actually reasonable performance for a low-cost meter, and is sufficient to detect most frequencies of RF typically encountered, except TV transmitters below channel 14, and FM and AM radio, which are below 300 MHz. Also not measurable are the not-yet-implemented 5G devices (up to 25 GHz).
When placed in an cage that is shielded from all RF, the 88Tplus correctly reads less than .001 mW/m² and it is accurate at frequencies around 2 GHz when the RF level is increased above zero.. There is a peak RF capture feature which displays the height of quick RF pulses (typically from cell towers, wireless devices, etc.). However, there is a problem with the way this peak capture is implemented-- the main displayed number shows each pulse height for 1/2 second before reverting to the actual RF field strength (a lower number) and the pulse height is also "permanently" shown a secondary number underneath the main number. If the pulses of digital information occur faster than 2 per second (typical of cell towers and routers), the main and secondary numbers both show the peak without ever getting a chance to show what the actual RF level is. Even the row of LEDs and the bar graph both remain elevated to the pulse height and there is no indication of what the average is, which is typically 1/10 to 1/100 of the pulse height. There is also no indication of whether the RF that is being measured is pulsing or constant. If you are only interested in the pulse heights (and not the average value) this meter works well on RF.
The E-field (AC electric field) measures the E field at 60Hz (North American powerline frequency) fairly accurately. At zero E field, the meter reads 2 V/m (volts per meter) instead of 0 V/m. This error is tolerable because the resolution is 1 V/m. (Oddly, the manual claims that the resolution is a more crude 10 V/m.) The meter is not equally sensitive at frequencies from 50 Hz to 50KHz, as the manual implies. Instead, at 3000 Hz, the meter reads ~1500% too high, dropping back to correct sensitivity at ~800 KHz. The E field is single-axis, in the same direction as the long dimension of the meter. A single axis sensor works well for E field, because the field is created by charged particles, or "monopoles" (electrons and protons). Simply point the top face of the meter outward in the direction you want to measure the E field, and the reading is generally correct.
If an E field source is due north of you, the field direction at your location will generally be along a north-south line. That is why you point an E field meter toward the source (north in this example). However, the correct measurement of magnetic field is more tricky, because magnetic monopoles don't exist. If a magnetic field source is due north, the field at your location may be north-south or east-west or up-down or even a diagonal direction. Therefore, if you point a single-axis magnetic meter toward a magnetic source, the meter may just read zero even if the field is strong. In order to measure this field accurately, you would need to point the meter in various directions until you see a maximum. This takes some time. The ED88Tplus is only single-axis in magnetic. It also reads 0.6 milligauss (0.06 uT) in a true zero field, and is therefore not usable below 0.6 mG. It also has a slow response time (~1 second) and the mG readings are only accurate at ~55 Hz (between 50 Hz and 60 Hz). At higher frequencies, it reads up to about 1000% high, and the 10mG overrange limit in the sensitive range is annoying.
Overall, the meter is good for measuring the higher-frequency RF, especially the peak height of pulsed signals. The electric field mode works reasonably well and is accurate at 60 Hz. The magnetic field mode, however, has multiple problems. The screen has good visibility in daylight and a backlight can be turned on for indoors. However, the screen is small and is in the form of square pixels. The numerals 0,8, and 5 run together and are difficult to read if next to each other. The manual is incorrect about certain specs and doesn't explain everything about the displayed parameters. Also, it has several grammatical errors and strange phrases. I would guess the writer's primary language is not English, which leads me to question the "Made in USA" printed on the back of the meter.
Full disclosure: I am affiliated with a US company that manufactures various lab instruments, including electromagnetic measurement equipment.
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