Tenma 72-7224, o/c 1283640

dsohal — Sun, 27 Feb 2011 01:33:03 GMT

Current Revision posted to Documents by dsohal on 2/27/2011 1:33:03 AM

1) The data-sheet from Farnell's site states that the upper Frequency Measurement is 100MHz, whereas the Operating Manual supplied with the instrument limits this to 10MHz.

--reply: Manual 10MHz is correct ,not 100MHz

2) And this is of more importance to me. On switch-on and selecting DC current ranges (40A or 400A) the display reads minus 1.7A changing to around minus1.4A after some time.

--Reply, pls adjust VR9 and VR6

Please confirm that, as the Manual (page 41) appears to say, that the 'RELdelta' key is used to actually ZERO the measurement system, PRIOR to attempting accurate measurement. As yet I have not set up a test circuit to compare the clamp-meter's measurement against a direct in-circuit ammeter.

--Reply, yes, pls press "Rel delta" key before measurement, if so, the obtained value should be more precise.

Q; Presumably your supplier is saying that, when powered on and switched to 'Amps' (DC by default), and 'REL delta' NOT selected, the display SHOULD BE ZERO, and if not, to open the case and adj. VR9 and VR6 to zero out the indication(s). This would be somewhat unusual on a (two !) new instrument(s), so please confirm / elaborate / copy me a schematic, eg. which VR for which range ? will upper measurement (span) accuracy be affected ? I do realise that the 72-722472-7224 is a low cost instrument but nevertheless (as an Electronics Engineer) would not, nowadays, expect 'zero errors' of this magnitude. Also, I can find nothing relating to this on-line".

Generally , we don't recommend to adj VR9/VR6 for end user as the stored value can be subtracted by press 'REL delta' before measurement( every time )to obtaine a precise reading .that is why we do not add the VR9/VR6 adj in user manual. however below information for your reference.

Yes, when powered on and switched to 'Amps' 40Vdc and 'REL delta' NOT selected, the display SHOULD BE around ZERO, and if not, to open the case and adj. VR9 (coarse)and VR6(fine) to approach zero.

Attached part location drawing you can find out where are VR9&VR6.

Attachments:

community.element14.com/.../72_2D00_7224.xls

72-7224.xls

Tags: 72-7224, tenma, o/c, 1283640