Test Equipment OWON XDM1041 Digital Bench Multimeter

Looks a good meter Chris! I have often wondered why most bench meters aren’t battery powered as well as AC, although saying that, do you remember that Fluke ex-military Nixie tube multimeter I got years ago? That had a battery option! Something daft like 30V…

it’ll be interesting to see how it goes, might be worth looking at how noisy the boost converter is, if it’s anything like those little USB power bank things they can kick out a load of hash just sitting doing nothing!

oh, I also have more multimeters than I really need! 3 bench ones, 2 Fluke handhelds, several other handhelds, a few AVO’s… I lost count!

 Regards 

Lloyd 

I too have lost count of my meters... I am hoping to eventually sell off numerous until I end up with my Amprobe analogue meter, an AVO 7, the Fluke 179 and my HP 6.5 digit bench meter.

I like your scheme there Chris, I'm surprised that they didn't include that option on what is presumably a relatively low power consumption device. "Bench measurements" can't always be "powered bench measurements"!

As to the meter collection here, well, the Fluke 83 and the Simpson 269 have "out of my cold dead hands" status, the others all have something to bring to the table- honest....

Curiosity got the better of me, decided to hook up the recharge/boost module, it was outputting 5.5VDC off-load. I set the pot for 5.0V off-load.

Posted by: @crustytv

Curiosity got the better of me, decided to hook up the recharge/boost module, it was outputting 5.5VDC off-load. I set the pot for 5.0V off-load.

Hi Chris, I used that very module in my geiger counter project. The step up converter is always running, and without load will flatten a 2500mAh 18650 in a week. I modified mine with a switch.. there's instructions here : https://andydoz.blogspot.com/2020/07/not-triple-tube-geiger-counter.html

The conversion of the OWON XDM1041, mains bench meter, to using a rechargeable/boost module was complete this afternoon. I also incorporated the @doz boost break switch, thanks for the tip Andy 👍 

A bit of a gaping whole at the back where the AC inlet used to be, but seeing a similar conversion elsewhere, this is a prime spot to incorporate a battery charge level meter.

For now, I'm very happy to have a nice portable bench style meter. Nothing that cannot be reversed, if I ever wanted to revert to mains supply.

Before & After conversion.

Rear  showing Boost output on/off & Font view, powered by the Lithium battery; original SMPSU removed.

Thought I would just do a quick comparison, of the OWON, using the MicroCal 1030 voltage reference, set to 500mV.  A gnats whisker,  between them. Clearly the Metrix is the most accurate, considering the kit I work on, this is pretty much a pointless exercise. Even the 1983 Fluke, is still a more than capable meter.

1. Metrix MTX 3281 (100k) count.
2. OWON XDM1041 (55K) count.
3. Peak Tech 3355 (6K) count.
4. Fluke 75.

Having another little experiment on converting the OWON bench meter that requires 5V as a power source.

What if you didn't want to spend the £20 as I did above to modify to battery use, what if you're not happy about using a LIPO battery & a recharge/boost board, is there another method?

Well, for a few pennies yes, or less if you've got the parts knocking about in stock (most of us have) how about a LM7805 regulator & 2 x 100n caps.

Yep, that works too, there is a 1.12V drop in supply on load, do I need to negate that, the meter seems happy enough.  The two 100n caps on the input/output are specified by the 7805 datasheet, I believe, to stop it going into oscillation. The regulator is only slightly warm to touch, possibly a heat-sink might be worth adding.

Off load & on load

Hooking it into the manual switch I added for the Boost regulator, isolates the supply. But there we go, three components and a standard 9V battery. Will it eat the battery any quicker than a normal handheld multimeter that uses a standard 9V battery? Perhaps, the LCD backlight can't be turned off, but you can reduce the brightness from High, to medium or low, we shall see how it performs.

Heat-sink added and LCD backlight reduced from 100% to 0%. At 0% backlight, it's still fairly bright, and now the on load voltage is 4.55V

Another alternative to using the 7805 is a high-efficiency replacement for the 7805. This tiny switch-mode voltage regulator allegedly provides a stable output of 5V @ 1A continuous load. No need to add a heat-sink, it's pin compatible with the 7805, and it's also the same size as the TO-220 package, so space saved. The module has thermal shutdown and current limit protection.

Quite a remarkable little package, I bought one for test, it will be here tomorrow, so will report back on how that performs too.

@crustytv 

Is it the PP3 battery voltage that’s sagging under load that is causing the low output voltage on load?

Hi Frank, Indeed, it would appear so. 👍 I'm now feeding the 7805 9V via the bench PSU. Off load, it's 5.7V and on load, it's 5.3V.

The backlight tests at 0% the load is 83mA, at 25% backlight load is 123mA, at 50% backlight 161mA, at 75% backlight 197mA, and 100% backlight the load is 229mA. You can track the voltage drop as the backlight is stepped up, via the Peak multimeter. It will be interesting to see tomorrow, if the little switched-mode voltage regulators, constant 1A load capability, will overcome that. Also, to see if the alleged high efficiency and low heat generation is true. The 7805 is producing about 44C.

@crustytv 

I can understand the offload being high, I know the 7805 needs a small load but still surprised at the voltage drop on different loads, I thought they were more stable than the test results show. Specification suggest regulation around 50mV.

Posted by: @nuvistor

[...] surprised at the voltage drop on different loads, I thought they were more stable than the test results show. Specification suggest regulation around 50mV.

OK, your observation made me revisit the little matrix board, Ooops, I did not have continuity to the GND pin, despite it looking OK 🙄 . Repaired, it now it behaves itself.  Full backlight and it's as good as 5V. Thanks for the reality nudge, Frank.

@crustytv 

👍

The little switched-mode regulators turned up, they are indeed the same size as the 7805 TO-220 package.

One was duly lashed one up with hook-ups to the OWON meter.

Initial observation, whereas the traditional LM7805 was bang on at 5V off load, and 4.99V on load, this package is down when off load at 4.97V, and down when on load at 4.89V. What is very noticeable is the promised lack of heat generation. Whereas the LM7805 was fairly hot, this little regulator runs cool to the touch.

Does it matter to me that the voltage is less than the stated 5V, for the intended use to power the OWON, the answer is no. Losing the excess heat generated by the 7805 is far more crucial, so this little package is ideal. If the intended use was for a far more accurate 5V, then maybe the LM7805 would have been better.

Left to its own, the little regulator, like the TP4056 based modules I used much earlier in this thread, will drain the battery. So again hooking it into the switch to cut the supply when not in use, is required.

In conclusion

Converting the OWON XDM1041 bench multimeter from AC supply only, to battery. The three options investigated were :-

1. Solution 1: LIPO £13.99 + Boost Regulator £2.19 Total=£16.18
2. Solution 2: LM7805 £75p
3. Solution 3: Switched-Mode regulator £2.64

1) Personally, I'm not a big fan of Lithium and their inherent considerations, and then there is cost, this being the most expensive for what it is delivering. That said, it did exactly what I wanted, provided a stable 5V supply, and had the convenience of recharge via TP4056 USB module. It does need slight modification to insert a switch to the supply, as the pointed out by @doz, the boost runs all the time, thus will drain the battery.

2) The good old LM7805. It performed exactly as expected (ignoring my initial failure to ensure GND), bang on the money for voltage, and importantly is the cheapest. However, the main issue was heat generation. Although not intense, it was still up around 44-47C, well under the 150C max stated on the datasheet. However, even at 44-47C, I felt this was not suitable for the confined space I had for the installation, being right behind the LCD display, I could foresee future problems.

3) The Switched-Mode regulator, same package size as the LM7805, but unlike the LM7805 produces no heat. Even at 3-times the cost of an LM7805, it's still very cheap at £2.64, and substantially cheaper than the LIPO option. The output voltage, although slightly less than specified on the datasheet, it's only .3V out of spec, and for my intended use perfectly fine. Like the TP4056, it needs a switch installing into the battery supply.

Note: Although options 2&3 are not rechargeable solutions like option 1, I'm happy with the trade-off. All my other multimeters are powered by 9V non-rechargeable, I don't see that as a burden to change when required. In fact, I can't remember the last time I actually changed one. If you really must have a rechargeable, then there's nothing stopping you using a normal 9V rechargeable.

Finally

The OWON XDM1041,in my opinion, is a very capable bench multimeter, having all the usual features, including math and record, with a 55,000 count. It's also, in my opinion, a very reasonable price at £99 delivered. The only thing I wanted was not being tethered to an AC outlet, portable is what I wanted. Unfortunately, OWON don't provide a battery option, hence this thread and investigation for a battery solution.

https://www.amazon.co.uk/gp/product/B09H2BTZNH/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

Hope this thread was of interest, and perhaps also useful.

@crustytv 

Heat is wasted power in this application so the battery should last longer.

Curiosity

No data came with the little regulator package, but I was interested to understand what and how it achieves, what it does.

SMD is way out of my comfort zone, but I thought I'd do a little research. Of all the ill's the Internet represents these days, as a portal to the good stuff, information, it is so very useful. Pre Internet, would have meant leafing through multiple pages of RS catalogues. Though I confess, I do actually enjoy that and own many period data books, using them frequently. However, as I don't have, nor want SMD data, Google was today, my friend.

What is at the core?

Having put the module under the scope, I was able to read the component ID's, well all but one, more on that later. At the core of this module, and pretty much in the centre of the board, is the HX1314G.

This is a wide range synchronous buck converter. The data I found states this step down regulator operates with an input voltage range, from 30V to 8V. The HX1314G achieves a 3.2A continuous output current with excellent load and line regulation. The switching frequency is programmable between 130kHz to 500 kHz. It further states it requires a minimum number of standard external components, which is self-evident from the low count on the module. The HX1314G also includes thermal shutdown and is 93% efficient!

So what are the other components?

Above the HX1314G is a component with "220" printed on it. This is a 7 mm 22uH (220) 2.5A high current inductor. There are two 33K resistors, these labelled "333". A single RB421D schottky barrier diode, 10V, 100mA, labelled "DC3". A single 100uF 16V electrolytic. Finally, one component I cannot identify, a beige block similar in size to the electrolytic. I thought it was a capacitor, but none of the meters that are capable, appear to be able to resolve it. I'm wondering if it is a cap, maybe it is to reduce ripple on the output.

I doubt anyone is interested in this info, but on the off chance someone is, well there you have it.

That brown thing is most certainly a cap, probably a multi layer ceramic cap, I recently used some in a pocket TV to replace some nasty aluminium electrolytic SMD caps that had leaked everywhere.

Regards,

 Lloyd