This came from eBay seller mywelllife for about $100 which is a very reasonable price for a flux meter with DC capability. This is a Hall Effect type meter similar to the F.W. Bell and Walker magnetometers. The price includes the probe making it an even better deal. But on the down side this is a strong field instrument, not suitable for measuring the Earth's field, but rather for measuring strong magnets. Also the instrument labels and documentation are all in Chinese.
This was made by Hangzhou BST Magnet Co. Ltd. I think what they call the HT202 is called the BST600 in the U.S.
Note: Although the above factory URL contains EN(glish). the amount of English is very minimal, to the point that you can't tell the difference between products. Also their on line form does not work and they don't have an email address so there's no way to contact them.
If you have an English manual please let me know.
The HT20 has two ranges 0 to 200.0 mT (low range) and 0 to 2000 mT (high range). This is equivalent to an overall range of 0 to 20,000 Gauss or 0 to 2 Tesla. The most sensitive digit on the low range will not detect the Earth's filed. This is only for strong magnets.
This model HT-20 has 3 push buttons and two analog calibration adjustments. There are other similar meters (maybe by the same maker) that have 6 push buttons and "Peak Hold" capability. That's a nice feature, but these units are priced around $400 about 4X what I paid for this one.
The probes for the BST600 and the HT20 appear to be the same. Each probe has a sticker with the Hall current (FIg 3 below) for that particular probe and the handheld tester has an adjustment to set that current. This current could be tweaked to calibrate the meter.
Using the same numbers as in the Mandarin manual:
1. 5-terminal probe connector
2. 4-Digit LCD with special characters
3. Pot (dial) to set sensor current (does not seem to make a change when turned + or - 30 deg?)
4. when Up: Magnetic field displayed, when Down: Sensor current in mA
5. Screwdriver zero adjustment pot
6. Range Up: Low 0 - 200.0 mT, Down: High (0 - 2000 mT)
7. Up: Off, Down: On
8. 9 Volt battery compartment lid
9. External 3.5mm power jack 9 VDC center positive (250 mA max)
So far the operation is based on the above controls and indicators since the manual can not be read by me.
The probe has a protective sheath that screws on and off to protect the probe when not in use. Do not put pressure on the probe or bend it since it can easily break.
Need to do some experiments with the AMY6 magnetic polarity tester to understand how to read polarity with the probe position. See Fig 5 & Fig 6 below.
When the black rectangle is up (black dot toward magnet) the N or S polarity indicator is correct. Also note there's a scale adjacent to the black rectangle (Fig 6) calibrated to 30mm. So if you can read the scale the polarity should be correct.
Fig 1 Included carry case
Fig 2 included wall-wart and all country adapter & probe
Fig 3 Probe marked "195" and when left botton
is down the meter reads 195 mA Hall current.
Fig 4 Haven't tried the zero adjustment
with jewelers screwdriver
Fig 5 Wrong polarity (S) when black dot is up.
Magnet polarity by AMY6 tester
Fig 6 Correct polarity (N) when black rectangle is up.
Note 30mm scale on top side of probe.
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