Data Logger

I had a job last week that needed a data logger on a sewerage pump station to monitor the running times during bad rainfall. I have a Hioki PQA / Data logger that cost an arm and a leg which I didn't fancy leaving for several days on site so I purchased a cheapie single channel current/voltage logger rather than chance my expensive one which was overkill for this application and it was also a bit on the large side to fit it into the control cabinet.

There wasn't too much choice available off the shelf where I live so I went with a ST-175 CV1 Data Logger, I think it's manufactured by CEM who are otherwise known as Shenzhen Everbest Machinery Industry Co. As you may have picked up if you're reading between the lines they're a Chinese manufacturing company and the particular item I purchased had no branding on it whatsoever apart from the model number. The price was ZAR 2250.00 which is equivalent to 120 UK quid and I don't mind admitting at this stage I was a bit nervous but it was supplied by a reputable wholesaler so at least there was a possibility of a refund if not satisfied.





What I got was a full kit with everything you need included, current clamp, voltage leads and clips, 2-pin power supply, USB cable, software disk, operators manual and even the AAA batteries. The case is pretty sturdy and in general the build and finish quality of the tester and the other components was good and solid.

One big bonus was the learning curve to use it was very quick, it took 10 minutes to install the software and driver on my laptop (WinXP) and everything just worked without incident. I set the logging parameters which is literally five selections when plugged into a laptop and I had a dry run in the workshop before I took it to site.

On site it took about five minutes to install the current clamp and the logger itself has a magnetic mount or hanger eye option on the back so it's easy to situate it.

The only thing I didn't like about it is to start the logging you need to hold the 'On' button in for 5 seconds until it shows 'Rec' on the screen (Record) but then you still need to press the Start button to start the actual recording process, I found this a bit unintuitive and clunky until I got a bit more familiar with it.

The logger was on-site for just over 100 hours (4.5 days) and because the pumps run for a minimum of 1 minute each time I logged run current at 5 second intervals to establish a load profile. It ran on the no-name batteries that it came with for the entire time and it used less than 50% of its memory capacity so I was very happy with its performance.

The control cabinet it was in was dripping in condensation all over the inside and whilst I put the logger in a fairly sheltered area of the cabinet it was very high humidity. Daytime temperatures reached the mid 30's and nighttime temps were as low as 12 degrees, there were also 2 large storms during the logging period and the unventilated cabinet was outside in direct sun and rain so conditions were pretty harsh. This seemed to have no adverse effects on its operation thankfully.

This logger has lots of limitations as well as a few nice features.

Limitations first, it's memory is adequate but if you want to log at a resolution of say 1 second for more than a couple of days you're going to hit it's limit. That said it has options on how the memory is utilised, you can set it to record in circular fashion so it continues logging indefinitely and starts overwriting the earlier data when memory is full. You can also set it to run until full then it auto stops.

The logger is only a single channel instrument so you can't log voltage and current simultaneously, you can only log either one or the other at a time. For commercial/industrial use where you want to see the current/voltage relationship this tester won't help you. In a domestic type application where you just want to profile a load for diversity or monitor a supply it's ideal. There are however other models of this data logger available which are 2 and 3 channel operation with larger memory capacity and 3-phase capabilities.

It would benefit from a wireless interface which would make harvesting the logged data easier especially if it's in the same location for extended periods. In all fairness it's asking a lot for something in this price bracket but I'd be willing to spend a bit more for that feature.

Some of the things I like about it in no particular order are;

• Good battery life.
• True RMS measurement.
• Good build quality.
• Good software.
• The kit is complete so no extra costs.
• Low cost
• Nice and compact, will fit in small panels or DB's.

The logger does have a high resolution waveform capture feature similar to a scope where you can take a hi-res sample of a voltage waveform for closer analysis. It's something haven't had time to test yet but it looks interesting and would be handy for testing dimmer output or battery charger outputs for example. I'll let you know more when I have some time to play with it.

Finally the software is actually a pleasure to use. Its simple, intuitive and it's fast. It takes under 30 seconds to capture the memory of 4 days logging and produce a graph. It has good zoom capabilities and gives all the general data such as max and min values, number of samples, start and end times etc off the bat. It exports the data to Excel format where it can be made into a graphed report. The same program then sets up the logger for its next task. Overall I found the software simple, focused, fast and a pleasure to use.

I'd say overall this logger is well worth the price, I already billed it out and covered my purchase price with a single job. The value for me is not having to use my expensive PQA on simple logging jobs where it's overkill and unnecessarily risky to leave it unattended. A surprisingly solid piece of equipment with a lot of uses for anyone in the electrical industry and at a very reasonable price.

I haven't been able to find these on the UK supplier websites so I'm guessing EBay might be your best bet if you're interested in one.

Here's the raw specs for the real geeks;

• Single channel input
• AC current clamp sensor
• Voltage sensor measures the floating voltage to meet CAT III 600V
• Digital LCD display to show some logging information easily
• Freely selectable measurement cycle from 1 second to 24 hour
• ACV/Load current/Leakage current measurement
• True RMS measurement
• Data memory
• Wave memory
• MAX/MIN, PEAK mode
• Time&date display
• Wave store
• Auto power off
• Download collected data through USB interface
• Manual and automatic mode
• Analysis software used to view graph for logging data
• Alarm display if user-defined maximum/minimum values exceed

• Reading memories: 100,000
• Measuring rate: 1 sec to 24h
• Analysis software: Windows98/2000/xp/vista (It might work on Win7 and Win8, i haven't tried it yet)
• AC current (True RMS): Range 2-200A, Basic accuracy: ¡À2%
• AC voltage (True RMS): Range 6-600V, Basic accuracy: ¡À1.5%
• Size: 114mm x 63mm x 34mm
• Weight: 248g

It certainly does not seem to be available in the UK directly, there seem to be a lot of Australian sites that cover that manufacturer.
They are available to buy in 1,2 and 3 channel from china sellers. cheapest singe channel would cost about £150.
But for the money that is not too bad, the 2 and 3 channel have a higher memory (luckily!)

I can find them on ebay for 200 USD which is a very similar price to what I paid. I haven't done much hunting so you may find cheaper.
Single Channel True RMS AC Voltage Current Data Logger 600V 200A USB Memory 100K | eBay

I saw the other models advertised but they're not available off-the-shelf in Africa where I am. The 3 channel might be worth a look depending on what you want it for and it does come with an appropriately larger memory capacity but I'm not sure that it will log current and voltage simultaneously in which case it might even be better to just buy 3 x single channel loggers like the one above.

I like it...now we're talking my language, why buy one when you can buy three.

Any options to log to a memory card or onto a laptop direct ?

Unfortunately it has no such options, it only has the internal memory register and can't accept a memory SD card. I haven't tried it to see if it will log whilst still connected to a laptop but I don't think it will.

Being able to add memory would have been nice but leaving a laptop connected for me would kinda defeat the object behind me buying it in the first place, I needed something small, simple and compact that was low risk to leave unattended for several days.

Here's some screen prints of the software;


This is a data set from a 22.5 hour logging session on a 2 x 5kW pump water booster station.


This is a zoomed in view on 30 minutes of the same data set. The screen shot doesn't do the graph justice, the vertical lines aren't jagged when you view the graph in the actual software. Some things that are evident from this view are firstly the very steep start indicates the pumps are DOL with no soft starts or Y-D starters.
Secondly the run current starts slightly higher and there's a slight decreasing trend as the pump runs and the head pressure increases, this is a typical centrifugal pump. Also it's a 2-pump setup and they alternate in operation and you can see the sight difference in run currents between the pumps on the graph. Both pumps are identical and running under identical conditions so this might be worth monitoring over time as a possible indication of something more sinister.


This is zooming in one one of the run sessions. Again the lines on the original graph are not stepped and jagged like they are in this screen shot. The vertical dotted line is where the mouse pointer was and the numerical info under the graph corresponds to this point.


This is just to give some idea of the simple setup windows within the software for customizing the graphing and for setting up the data logger for a logging session.

Coincidentally I have just bought this

[h=1]Extech DL160 Dual Input True RMS AC Voltage/Current Datalogger[/h]this is like yours but has two channels.
from what I can make out, it is an American manufacturer.
I have got it fitted at the moment, and I'll be going back to retrieve it and download the data, this weekend.
I read your post with a bit of trepidation and was relieved to see you were positive about the Datalogger.
Nothing more annoying than shelling out on something only for it to turn out to be crap!

tigerpaul said:

from what I can make out, it is an American manufacturer.

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I'm not sure but I've got a feeling the Extech may be a rebranded CEM which is very much Chinese. I know from some of my other testers there's some Brymen multimeters are identical rebrands of Extech and the waters about who manufactures what get a bit murky. Sometimes they're just rebadged and sometimes they share the same PCB and internals and come in a slightly different case and button layout.

The tester you have looks identical to mine except you have the two-channel version and mine is only single channel. I don't think you'll be disappointed, I certainly wouldn't class them as crap. Mine is on it's third week away from home and it's been doing just fine. I have to be honest and say for what you pay they're good value, you get a complete kit that does exactly what it says on the tin and has a million and one everyday uses.

I'd be interested to know if you bought it through a shop or was it an on-line supplier? I think if I was in the UK I'd be a lot more concerned about getting it annually calibrated and certified. We are registered and authorized to self calibrate our own instruments but with this kind of datalogger the applications I'd use it for wouldn't require it to be certified accurate but those requirements might not hold in the UK.

This is one of the biggest problems with this type of instrument is usually I'd have to purchase it on-line because there's so few off-line distributors like wholesalers etc that sell them in South Africa. An on-line purchase is far more problematic for me because you're unlikely to get after-sales service such as tech support, spares and repairs and certified calibration. It's a shame because manufacturers like CEM have a great range of product and usually at very reasonable prices and as a company they seem to have a good track record but without the physical presence of the company or its official agencies in a country it always makes it a less appealing purchase option. I guess for now I'll just enjoy drooling at the catalogue .

Let me know how you find the data logger after you've used it, feel free to add to this review if you like.

I very nearly bought one of the recommended data loggers but came to my senses in time (since I have no money) but it was tempting; If they had had the three channel one I may have been ruefully looking at an empty bank account and a very unlikely to be used logger.

Still, one day.

I was going to be polite and not be so base as to ask the price that Paul paid for his 2-channel version....but what the hell, c'mon Tigerpaul, tell us how much it cost

I'm on the market to getting a DATA Logger in the near future, I've spotted a neat 4channel device that does all this but each input is bought seperately but they have data logging for multiple input use like Temp', Speed etc as well as Energy monitoring.
I'll look into it a little more and if I get on I'll add to the thread about my findings.

This is what interests me if anyone ever used one?

HOBO® UX120-006M Analog Input 4 channel Data Logger

I also looked at what I classed as environmental loggers as an option but I already have a small temp logger and there's never been an occasion where I've needed to log speed. I also liked the wave capture feature that the one I purchased has, although I haven't had a chance to try it yet, I figured I was a lot more likely to benefit from that more than I would benefit from other stuff.

Price of your option is certainly competitive being a 4 channel device for just over a hundred quid. I think you need to purchase the cables and clamps separately however and at 80-100 quid each for the split core CT's and 10-20 quid each for the connecting cables I think it might work out expensive in the end. I'm also not sure about the construction being very site-friendly, it looks a bit domestic to me but I wouldn't pass judgment until I'd actually had my hands on it.

Also that site you linked to sells the software for 88 quid whereas it appears to be for free here. There's also a full user manual available at the site I linked.

Marvo said:

I was going to be polite and not be so base as to ask the price that Paul paid for his 2-channel version....but what the hell, c'mon Tigerpaul, tell us how much it cost

Click to expand...

It was on tester.co.uk for £190+Vat, but I bought it with a few other bits and pieces and got it for £179+vat