I recently purchased a digital multimeter from Maplin which was on sales at that time: Precision Gold N56FU. Being a full sized autoranging multimeter with computer interface, this meter £44.99 seems to worth every penny. Of course, Maplin didn’t make this meter. Some Chinese dudes did. Maplin just rebranded the meter because E-SUN sounded too lame =P
No purchase is complete until it is disassembled!
Nope, certainly no FLUKE board, but still, it looks very solid.
1. The controller: FS9922-DMM4 from Fortune Semiconductor Ltd. You got to love those Taiwanese. They slapped two analogue to digital converters, voltage regulators, AC rectifier, LCD driver, RS232 driver, etc etc…onto a silicon slab. That’s basically EVERYTHING you need to create a modern digital multimeter on a single chip!
2. Infrared LED: If you’re wondering why there’s an infrared LED on the meter, trust me, you’re not alone. I was puzzled as well. Note: I removed the complimenting infrared receiver module for clarity reasons.
3. True RMS converter: AD737J from Analog Devices, which a quoted accuracy of ±0.2 mV. Sweet!
4. 640 mA fuse: To protect the micro/miliampere line.
5. 20 A fuse: To protect the 20A line.
6. Copper jumper: Well, if you want to pass 12 kW of juice through this meter, the bigger this copper jumper, the better.
Look at the huge fuses!
The brain!
True RMS converter
Infrared LED
Infrared receiving unit. Notice the Silicon Labs CP2101 USB-to-UART converter chip (2). The IR receiver is located at (1) and the USB port at (3).
If you were still wondering why on earth did E-SUN used infrareds instead of just hard wiring the the USB-to-UART chip to the controller, consider this: You are conducting a high voltage experiment. Due to budget cuts, your department crossed out FLUKE and gave you an N56FU instead. You hooked the meter up to the 415 V rig and connected it via USB to a £1500 notebook. You took the notebook and went behind the plexiglass shielding for protection.Your computer started charting impressive graphs of the equipment you were working on when suddenly, there was a flash a light and you get thrown ten feet away. Your meter was fried and so was your notebook. The plexiglass shield was still intact though….So what happened? Some incompetent lads wired your rig wrongly! A gazillion volts rained down your meter due to a premature capacitor discharge. The current travelled through the multimeter, through the USB cable, over the plexiglass, straight to your computer! Whao….busted!
Back to business! This is what we call Optical Isolation. The circuitry on the mainboard (1) converts RS232 to IrDA signals and beams it to a receiving unit (2) housed in tough, clear polycarbonate. The IrDA signals are then decoded and converted to a USB language that your computer understands. Note that there aren’t ANY electrical contact points between the mainboard and receiving unit. The circuitry on the receiver draws current from your USB port only, since high voltage electricity can still arc and jump into this circuitry if it isn’t 100% isolated. This way, you and your computer can remain safe (while the meter literally takes all the bashing).
Owing to the fact that this meter can do MORE things than a £150 FLUKE 116, and that SAFETY has been heavily emphasized, I would say this is the most value for money digital multimeter EVER.
Have to agree – they were selling this reduced to £29.99 at local Maplins recently and I think I got the last one. Seems to be well engineered and has great specs.
My only complaint would be it seems slow to equilibrate (maybe this is only on the most sensitive ranges?).
Hopefully this low-pass filtering is absent on the USB uplink, have yet to investigate this.
__Mark
Nice and useful review, I also own one of these multimeters and I am extremely happy about it.
It works with both Linux and Macs, and the USB data stream is easy to read. Sweet! D.
Fully agree. A clever piece of measuring tool it is (was, in my case. I managed to fry my N56FU with a too high of a voltage, most likely static, that it couldn’t take).
I own one this multimeter as well and is working quite good. Unfortunately I lost CD with software for this multimeter do someone have idea where I can download this software (for windows) or maybe someone can upload it for me. thanks
Question: When selecting Capacitance, should the meter be showing zero’s, the reason for my question is my N56FU meter is always showning a reading of about 317.00 I believe someone who I work with (he thinks he’s the Oracle) did not bother to discharge the 3300uf cap before tesing it, is there any way I could repair it.
As: here you go http://rapidshare.com/files/385306021/n56fu.zip
john: unfortunately it doesnt seem possible to me. Looks like you’re gonna have to go oldschool with RC circuit and a stopwatch lol
Thanks for the info on this dvm. I also bought one when it was on offer and have been very pleased with it till now. However, I just trashed it completely with overvoltage (from an electric fence – utterly stupid thing to do!). I thought there was no voltage on the fence – wrong – I saw a reading on the volts range, and then the display went blank. Disconnecting the battery and reconnecting makes no difference. Have you any thoughts on what might be dead? I cant see anything trashed inside but presumably ESD could have got right through to the main processor chip – can this device be obtained in one offs? Its probably not worth the effort of trying to repair anyway – at least I now have a nice USB serial infrared receiver for another project – does anyone know what baud rate it runs at?
Tony
Whao! thank God you didn’t use your fingers to test it though =P
The USB receiver seems to be operating at 2400 baud, 8 bits, no parity, 1 stop bit, hardware xon/xoff.
Hope that helps!
How accurate do you think the temp sensor is on this thing ?
Toby: I’ve calibrated the multimeter against a benchtop thermometer using the same thermocouple before. It appears that the multimeter has rather bad linearity, especially towards the extreme ends of the scale. I don’t have the exact numbers with me but I would say for scientific use = no, for casual use = yes.
Great value for money, I paid €30 for mine (on sale). Although beware when continuity testing -I just spent a few hours looking at a board (pulling my hair out )trying to figure out where a short was only to find out that it considered a 10 Ohm resistor a short, head recking!! Maybe this is standard I dont know….
Any one know of any software to force it to grab a reading rather than the time interval the supplied software has?
In fact is there any better USB Windows software available for this beast?
Is there a API Dll available for this meter?
I’ve just bought an N56FU but can’t get it to talk to my Windows 7 PC
I’ve tried installing the drivers (winnt) using CP210xVCPInstaller and also run the setup on the CD and repeated the whole thing using a version downloaded from the web. The software runs but won’t read from the meter. I would be grateful for any help/suggestions!
Just bought the meter from Maplins but cant get the software to fire up it just gives a demo page with a resistance (ohmeter).
I looked into the drivers and files and it seems to support Windows 98me and Windows NT.
So maybe thats what the problem is, has anyone got a suggestion?
are there any driver updates?
The Maplins guy said I need to buy a battery with it but I installed the one supplied and its got a voltage 0f 9.6Volts off load which seems ok to me.
Hi gain – sorry if I seem pushy but I’m nor sure if my lasy query got through (I haven’t had a confirmation) I installed the link software (Windows 7 64bit) but it doesn’t pick up readings from the meter. Does anyone know if it’s a Windows 7 problem or might the meter be faulty? Thanks in advance
Dave: I’ve got several of this meters hooked up to Win7 64-bit notebook using driver from http://www.silabs.com/products/mcu/Pages/USBtoUARTBridgeVCPDrivers.aspx . Hope that helps
Gadgetboy: Use the above link for driver =)
Quatermass: I’ve not seen any WinDLLs but Linux modules are available (QtDMM2). You may be able to code a interface yourself using pages 31 onwards of http://www.ic-fortune.com/upload/Download/FS9922-DMM4-DS-11_EN.pdf
Hi LordTCT – Thanks for helping:
I downloaded CP210x_VCP_Win_XP_S2K3_Vista_7 and ran it: it installed in c:silabs\MCU\CP210x\Windows_XP_S2K3_Vista_7 with the following folders: x86 and x64 and the files: slabvcp.cat – slabvcp.inf – setup.ini – Release Notes.txt and CP210xVCPInstaller.exe
I ran CP210xVCPInstaller.exe and it reported a successful install (files appeared in C:\Program Files (x86)\Silabs\MCU\CP210x including the x86 and x64 folders and slabvcp.cat and slabvcp.inf
I then ran N56FU Communications Program V1.52 and connected to COM3(USB)
The program is frozen in a resistance mode, with a reading of around -15 ohms regardless of what I try
I’ve pressed the Rel/USB button on the meter but it just puts it into the relative mode
I’ve tried two connection cables but to no effect. My black probe is in the COM socket and the red is in the righthand-most socket.
Am I doing something silly?
You need to push and hold the USB button for a couple of seconds until USB comes up on the screen.
Lord TCT,
how did you hook up more than one meters to you laptop? I have been trying for days without success. I found the n56fu software is not useful for multiple meters. It would not install more than one copy, it would not run two instances either because it uses the same data file. tried a few other ways such as run as different user and start up from different directory, all failed.
thanks for any help you can give me.
daniel
Hello Kent,
I’m afraid I’m not the manufacturer of the product so I’m unable to give you detailed troubleshooting steps =(
If I were you I would plug the unit to a PC, switch to USB mode and intercept the signals using a terminal application (such as Hyperterminal for Widows or Minicom for Linux). From there you will be able to see if its the driver that’s giving problems, or the the multimeter is giving you corrupted data.
Cheers!
Daniel,
I wrote my own RS232 wrapper using C# (Microsoft .NET) for multiplexing. It’s pretty simple. For starters, you may want to try using WinForm’s the Serial Port component to interface with your meters and once you are able to read the meter’s sentences, you should refer to the manual below on how to interpret them:
http://www.ic-fortune.com/upload/Download/FS9922-DMM4-DS-11_EN.pdf
You’re gonna have to code your own data logger and visualiser of course, but .NET 4.0 has a pretty useful X-Y scatter chart component built in.
Crash Override – Thanks very much! It works. Now I know what I’m supposed to do, I lookedf at page 9 of the instruction booklet where it states . . . Pressing and holding this button for about 2 seconds sets the meter to USB communication mode . . . ! I was initially thrown by page 33 which says that there are instructions on the CD (which there aren’t!)
Again – thank you!
Thanks again Lord TCT for pointing me at updated software!
Thanks for posting your article and the links. They provide fascinating insights to the innards of this remarkable meter.
Through use, I’ve found that the N56FU has a bug which can rapidly discharge the meter’s internal 9V battery. When measuring with the meter, if you use the screen light, then wait for the light to time off, then press max/min (twice if max/min not previously pressed), the meter draws more than 40mA from its internal 9V battery. The only way I’ve found to stop this high current drain is to move the function switch to OFF.
Thanks for the tips Clive! It should also be noted that the screen light is very power hungry – draining a carbon-zinc battery in just 5 hours on! I think I’ll be replacing the white-ish LEDs with more power friendly yellow LEDs!
The screen light bug can be avoided if the light is turned off manually (press Hold/Light button for > 2 seconds) before the light times off (10 seconds). Once the light has timed off automatically, a subsequent press of any button is likely to initiate the bug causing a high current (>40mA) draw from the 9V battery. Once started, the high current draw continues until the function switch is moved to OFF; whether or not the lamp is on. When employing the manual light switch off workaround, the meter uses about 10mA when the light is on, and 4mA when the light is off.