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PZEM-016 single phase modbus energy meter

Just saw this today on ebay :

With a lot of function and for $10 seems a great deal.
Any one tried it already ?

Specs:
PZEM-016: Measuring Range 100A (external transformer) With Split CT

Specifications:
Voltage:
Measuring range:80~260V
Resolution: 0.1V
Measurement accuracy: 0.5%

Current
Measuring range: 0~100A
Starting measure current: 0.02A
Resolution: 0.001A
Measurement accuracy: 0.5%

Active power
Measuring range: 0~23kW
Starting measure power: 0.4W
Resolution: 0.1W
Display format:
When the data is <1000W, it display one decimal, such as: 999.9W
When the data is ≥1000W, it display only integer, such as: 1000W
Measurement accuracy: 0.5%

Power factor
Measuring range: 0.00~1.00
Resolution: 0.01
Measurement accuracy: 1%

Frequency
Measuring range: 45Hz~65Hz
Resolution: 0.1Hz
Measurement accuracy: 0.5%

Active energy
Measuring range: 0~9999.99kWh
Resolution: 1Wh
Measurement accuracy: 0.5%
Display format:
When the data is <10kWh, the display unit is Wh(1kWh=1000Wh), such as: 9999Wh
When the data is ≥10kWh, the display unit is kWh, such as: 9999.99kWh
Reset energy: use software to reset.

Over power alarm: Active power threshold can be set, when the measured active power exceeds the threshold, it can alarm
Communication interface: RS485 interface

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Interesting I guess. You can hardly buy a CT for that, but a couple of comments:

I have some pzct-02 CTs and have tested them. They saturate at about 50A at 60Hz. They state 100A so maybe they have beefed them up? (doubt it).

The device connects directly to the wall AC. I’m guessing there is no UL or CE on this.

All that said, there is a market for everything.

That’s very much a function of how big a burden R you make them drive. How big did you use?

Yes, I’d definitely be cracking it open and seeing how good a job they did on isolation before I went anywhere near those RS485 connections. There’s a pic of the guts here:

https://www.alibaba.com/product-detail/New-AC-100A-Single-Phase-Multi_60754182945.html

If it’s like the rest of their (Peacefair) product line, there is no isolation.

I have one of their PZEM-004 units. It uses a capacitive dropper to connect to the mains.

Spec’d burden is 10 Ohms:

If you zoom in on that PCB photo in my link above, I think you can just about make out the barrier. I think it runs horizontally across the board at the yellow SMPS transformer. I think those two white 4-legged ICs on the left hand side are opto couplers. They and the transformer straddle the barrier. Everything above that is live and I suspect is where all the monitoring gets done. The smaller bottom section is basically the isolated serial interface to the outside world. So, depending on clearances, it could well be legit.

There are apparently 2 versions, the 014 has an internal shunt and is connected in series for loads up to 10A and the 016 uses an external CT to read up to 100A.

This link has a bit more info

http://kimgrity.com/ac-communication-module-c-64/pzem016-ac110-220v-100a-power-monitoring-voltagecurrentactive-power-meter-with-rs485-interface-communication-p-693.html#.WzdO_6dKguU

it says the 2 models share the same “communication module” and details the modbus registers etc. it implies you can have up to 246 of these connected via modbus-RTU.

It also shows them as having opto-couplers (see the block diagrams) and I notice there are ce and fcc logo’s on the labeling on the underside of the case with the connection diagram.

I also found this zipped info, the Word doc seems to be the same detail as on the webpage I linked above, but i haven’t looked at the rest (open at your own peril!)

PZEM-014 and 016 software in English.zip (2.2 MB)

I got the following link and password from this web page https://www.alibaba.com/product-detail/New-AC-100A-Single-Phase-Multi_60754182945.html and downloaded it before it disappears as I have seen other links and passwords to baidu that have expired already.

Link: https://pan.baidu.com/s/1B0MdMgURyjtO1oQa2lavKw
Password: ytkv

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… and there is 2 versions of the 016 too, with a split core CT or with a solid core CT.

I just ordered one of these to play with (for £7.76 incl shipping! shocking!)

https://www.aliexpress.com/item/Digital-Energy-Meter-AC-80-260V-100A-Voltmeter-Ammeter-Voltage-Current-Power-Tester-RS485-Modbus-PC/32869121338.html

I was hoping we might be able to swap the CT’s (different physical sizes) and re-calibrate, but it seems the calibration process is just to hook it up to a 220V supply and 1A (presumably unity) load and trigger the calibration process with a password, the only detail I can find is “it takes 3-4 seconds”. That would suggest these can only be calibrated with a calibrated fixed reference supply/load which isn’t ideal. They do (obviously?) come factory calibrated.

I just realized the “+5V” terminal alongside the RS-485 “A”, “B” and “GND” connections is an output, not a input to power the isolated RS-485 module.

Pro’s
No need to provide external 5v, particularly good over long runs.
Potentially power either an esp8266 with a modbus sketch or an Arduino type board with either RFM or Ethernet or even LoRaWAN perhaps?

Con’s
Is it as isolated as expected?
100mA might not be quite enough for some ancilaries

What would be the situation with installing this on a high current circuit at the remote end? Obviously a 63A cable is not going to fit the terms, so will using a smaller gauge wire to link this to the load’s supply terms be a problem? Would an in line fuse be acceptable if this is mounted very close to the load or would a separate fused spur need to be run?

I’m just thinking of an application I have where we monitor several MVHR units separately, currently because of the shared MCU and AC adapters, all the CT’s are at the dist’ board and it gets a bit messy with all the other monitored circuits too. I’m wondering if (for example) we could fit one of these to each MVHR unit (prior to installation on site) and just daisy chain a Cat5 cable to all the MVHR units once they are installed, that might be much easier and neater too.

Wouldn’t that wire have the CT clipped around it and the CT’s leads be connected to the terminals?

The USB to RS485 converter (at least the one pictured) is powered from the USB port. (I have several of them)

The monitor also needs a mains voltage ref, so it is connected directly to the AC supply too, not just a CT. Ideally you would source that AC connection from the same wiring that you are monitoring (the CT is on) but with a 100A max for the CT, that approach could leave you with this device only protected by a 100A breaker (or higher). I’m questioning whether the size of the wiring between the load terms and the monitors AC terms would dictate the breaker size ie downsized to the thin cable capacity, which will then be of no use for the load.

There used to be a dispensation where a wire less than 2 m long inside a “switchboard” need not be fused at source.

I’d interpret that as saying you can have a short wire - in this case inside the installed equipment - running from the incoming line terminal to the voltage monitor, and provided that it’s physically protected from damage during installation, that’s OK. It would assume that the energy meter itself has internal protection against a fault, e.g. a fuse or the isolating transformer has a thermal fuse buried in the windings. If it has none of these, a fuse/mcb is required anyway.

That’s great if you are using a USB to RS-485 adapter, and even then, you need to power the device that powers the adapter. in theory a esp8266 (for example) could be a master and get powered by one of the slaves +5v output, no USB or external 5v required.

In or on depending on whether the supply is directly to a PCB or warranty rules prevent opening the unit etc.

Otherwise that sounds fine, yes it would be as short as possible and we can add a in-line fuse and/or conduit (if it is mounted external) etc.

Ahh, right. Gotcha.

On this side of the pond, a fuse or breaker would be required to feed the device.
As you mentioned above, an inline fuse at/near the load would be required.

Hmm, You may be more correct on that than you realize. :wink:

The espressif website says the esp8266 draws 120 mA when the output is at +13 bBm, which is the lowest value shown on the chart. (170 mA at +17 dBm) If the output could be turned down a bit more, that might help – at the expense of operating range.

Ref: https://bbs.espressif.com/viewtopic.php?t=133

If the 8266 were powered from the same supply that’s powering the device, et al, then, of course, no issue.

Just for the hell of it, I ordered one too. Already have three modbus devices, so figured adding a fourth
should be easy. It’ll be interesting to see how it compares to my WattsOn power transducers.

Even if it’s junk, at 12 bucks, it’s a throw-away item anyway.

Yeh, I thought the esp8266 might be 120mA or there abouts, I’m sure I’ve read that somewhere here with ref to the emonESP. I doubt I would personally go that route, it was just an example. However, I do now wonder IF there were several slaves daisychained (including the 5v terms) if you would effectively have No of slaves x 100mA on tap for powering the master? Depends how isolated those outputs are I guess?

Not sure what you mean there, by “the device” are you referring to the monitor? That’s limited to 100mA. Or are you refering to a “master” device with it’s own supply? I was suggesting using the esp8266 AS the master and powered via the slave(s).

My point was that if the slave(s) can power a simple master and communicate with the outside world (eg post to emoncms or emonhub) this is a totally self-sufficient monitoring solution, no additional AC adapters required (9v AC or 5v DC), no additional CT’s, no sockets to be installed for those plug-in adapters and no additional hardware to plug a USB adapter into or power supply for that device. But, although there may be a cost/space saving due to low component count, it is not something that a casual “DIYer” could easily install, because of the lack of plug-in adapters.

That was my thinking, I have no Modbus devices at home, so even if this turns out to be useless as a monitor, I will have something to develop Modbus applications with and test hardware/adapters etc for not a lot of money.

I was thinking of your comment:

I should’ve said: e.g. a RasPi. Sorry for the ambiguity.

Yep. That part would be nice.

Not necessarily unity. When I put mine into calibration mode, it expects 230V, 2A with a 60° phase shift as recommended by the energy IC manufacturer. Any introduced phase error becomes much easier to spot once the two sine waves are offset from each other.

Just ordered one to test.
I see the module wifi autonomous modded with an esp8266 put inside the box.
If anyone will be developing code for this, i’d be interested to test.