F W Bell mA2000 low current clamp with built in meter and O'scope output - Page 1
Forum section: electronics / testgear

author: Fraser
author_rank: Super Contributor
timestamp: August 29, 2021, 07:30:12 pm
content: I recently purhased a very nice MICSIG AT1102 tablet format oscilloscope. I wanted some specialist accessories for it and these included a low current AC/DC current clamp.I purchased a Hantek CC-65 as a relatively inexpensive current clamp for automotive and electronics work. I shall be modifying the CC-65 to improve its performance as detailed in the CC-65 thread on this forum. Some time ago I had seen another current clamp on ebay that interested me, but it was just a little too expensive for me at the time. I revisited that sellers auction recently and managed to negotiate a small price reductionThe unit was mine. So what is it and why is it interesting ?The unit is a Bluepoint (Snapon) EEDM511A non contact Current meter/clamp/scope probe. This unit comprises a two range LCD True RMS current meter and separate current clamp. It measures from 0 to 2000mA AC/DC and offers a bandwidth of 100kHz for the LCD meter and Analogue oscilloscope output.This unit is not made by Snapon or Bluepoint, it is actually a product from the much respected F.W.Bell instrument company and called the "mA-2000" in their catalogues. This explains the high quality of the design. The unit can operate as a non contact True RMS current measurement meter using the built in LCD display or an oscilloscope may be attached to the base unit in order to view the current waveform and make measurements. The specifications state a noise level at the Analogue oscilloscope output of less than 100uV !I would not be surpised if this unit is not well known. I certainly had not seen it before but can see that the F.W.Bell branded unit is more common and is identical to the EEDM511A except for labelling.I attach pictures from the eBay auction, including from the user manual. I will also add pictures of the F.W.Bell version.This unit will be perfect for non invasive low current draw meaurement and where low noise waveform display is important.My unit dates back to the early 2000's and I am uncertain whether it is still available new. On the used market the price varies greatly but is usually quite high. New price was around $1K. My 'as new' unit cost me £80Specifications:Ranges:Low (200mA) 0.1mA to 199.9mA DC or RMS ACHigh (2000mA) 1 to 1999mA DC or AC PeakAccuracy% of reading +/- 3 counts for the displayed reading or +/- 0.15% of range for the analogue output.DC: 1%AC Low 2%AC High (200Hz-400Hz) 4%AC High (400Hz-40KHz) 2%AC High (40KHz- 100KHz) 3%Repeatability0.5% of reading +/- 3 counts for the displayed reading or +/- 0.15% of the range for the analogue output.Output NoiseLess than 100uVFrequency RangeDC: 0Hz to 200HzAC Low 0Hz to 200HzAC High 200Hz to 100KHzFrequency Response (-3dB point):AC Low 400HzAC High 250KHzRise TimeAC Low 750uSAC High 1usAnalogue Output scaling1mV/mAAnalogue output Load10K Ohm min, 100pF maxCurrent . Frequency Limit80A.KHz maximumProbe inductanceLess than 1uHFraserUpdate…..Not mentioned in the specifications but detailed in the user manual : The maximum voltage on a measured conductor should not exceed 300V DC or RMS AC. The conductor should also be insulated.

author: Fraser
author_rank: Super Contributor
timestamp: August 29, 2021, 07:32:56 pm
content: Pictures of the F.W.Bell version.....Note: F.W.Bell became Sypris Test & Measurement.

author: Fraser
author_rank: Super Contributor
timestamp: August 29, 2021, 07:52:14 pm
content: The mA-2000 User manual from F.W.Bell plus the calibration manualIt is a good sign when a manufacturer is willing to provide the calibration procedure for their equipment

author: Fraser
author_rank: Super Contributor
timestamp: August 29, 2021, 07:55:08 pm
content: mA-2000 Datasheet

author: Fraser
author_rank: Super Contributor
timestamp: August 29, 2021, 08:09:02 pm
content: Regarding the type of current sensing used in this meters current probe head, I believe that it is a Closed Loop compensated Hall Effect device design. This is detailed by F.W.Bell in their various papers on Hall Effect current sensors and meets the needs of this low current probe.Fraser

author: tautech
author_rank: Super Contributor
timestamp: August 29, 2021, 09:01:34 pm
content: Only in the manual was the insulation rating.Then there are some hooks which one needs to take note of for general electronic use as the stated design is for automotive use:Do not clamp around conductors with voltages equal to or exceeding 300 V dc or rms ac.Then later the nitty gritty:Do not clamp the probe around bare conductors. Conductor must have a suitable insulation.Care needs to be exercised for any HV use.

author: Fraser
author_rank: Super Contributor
timestamp: August 29, 2021, 09:14:34 pm
content: Tautech,Damn I forgot to mention that important detail. Yes, this unit is designed for use below 300V DC or RMS AC. Not an issue in my use scenario but could be important to others. My use will be on wires carrying less than 50V.It is the very low current measurement and monitoring capability that most appeals to me. This will be great for monitoring the startup DC current waveform of thermal imaging cameras etc as that can tell you a lot about some faults. It may also prove useful for monitoring the current draw on battery powered equipment or <2A charging circuits without having to break the power path to insert a meter in series.One use that I have seen mentioned but had not come across before is monitoring of RS232 communications cables. The MICSIG AT1102 has a very nice RS232 protocol decoder built in that presumably could read the data on the TX or RX leg without a physical tap into the line.It is early days for me with the unit but it does seem somewhat unusual and low noise. Hence why I am posting about it here on the forum.Fraser