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Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

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    Successor to Fluke 225C scope or equivalent for Profibus signal analysis?



    Hi, I saw the handheld Fluke 225C scope and it looks great for troubleshooting bus systems like Profibus DP.
    But it's been discontinued.

    I found the recently released Fluke 125B which also has this system which Fluke calls "Bus Health Test"
    But compared to the old 225C it's very limited in bandwidth (40Mhz vs 200Mhz) and therefore not really something I feel is worth $2000

    The new Fluke 190 Series II scopes seem great, I especially like the ones with 4 input channels, it could be very useful to me.
    But they have dropped the "Bus Health Test" in this series, or atleast not released a model with it yet.
    Anyone got some ideas on why this is?

    Just for info the old 225C scope was based on the 190C scope, i.e. it the bus test was just a feature added and to differentiate it they gave it a new model name...

    I know there exists dedicated Profibus testing equipment and while that might be a good way to go as well for me a scope which can be used for so much more seems a better investment.
    Attached Files
    "The one who says it cannot be done should never interrupt the one who is doing it."

    #2
    Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

    after my pm97 blew up (literally with vapourised tracks) i wouldnt trust scopemeters.

    Comment


      #3
      Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

      You should give Fluke a call. Tell them what you want and see if they have something coming out soon. Also, if you tell them you want the bus health test you never know they just might add it back.

      Comment


        #4
        Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

        Yea I sent Fluke Sweden a mail, no reply yet, might try Fluke US instead.
        Was actually troubleshooting a Profibus system today, had to use a scope to find the cause of the problem.
        A Siemens encoder had deformed it's PCB against it's casing and the copper layers in the PCB was therefore shorting to ground!
        Of course all the other devices in the machine was throwing errors except this one!
        Attached two pics of the waveform after I fixed it, amazing that it works so reliably when the waveform is not better!
        Attached Files
        "The one who says it cannot be done should never interrupt the one who is doing it."

        Comment


          #5
          Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

          Give them a call. Sometimes people will not respond to email. Sounds like a sneaky problem. Are the waveforms just not triggering properly?

          Comment


            #6
            Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

            You are correct that the scope is not able to trigger on the waveforms properly.
            I spent an hour this morning just testing on another machine but was unable to get it cleaned up.
            If I pause the signal it's correct but not during playback, so maybe the scope is simply too slow to do it, I'm not sure.
            I also noticed that when I simply move the vertical position up or down it introduces noise. (Even with no probe connected).
            So I guess something might be amiss with the scope I borrowed...
            Of course the small pigtail I hacked together might not be optimal.
            (Hence why I named the picture "Antenna-Setup" in my previous post )

            I found the following from Profibus about what scopes they recommend to use.
            Of course that does not involve things like the Fluke "bus test" which is something completely different.
            My searches so far have not turned up any other manufacturer that offers similar functionality like Fluke's "bus test" feature.

            4.5.1 Technical Prerequisites
            The following characteristics require an oscilloscope for measurements on the PROFIBUS.
            • Design: Digital storage oscilloscope
            • Bandwidth 100 MHz
            • Channels: 2, potential separated to each other and against the device ground (network connection)
            • Trigger: Internal + external
            • Coupling type: DC

            Battery-powered oscilloscopes are well suited. Due to the handy format and independent power supply they offer a high level of mobility in the system. The potential separation between the two input channels and against the device ground is particularly important. Separation of the two channels ensures that they do not affect each other. It is just as important that both channels are also potential separated from the device ground. If this is not the case, then an unintentional or intentional connection of a channel ground to a live core can result in a short circuit. For measurements on the PROFIBUS, often the channel reference potential is connected to one of the two data lines. Measurement would not be possible without a potential separated oscilloscope, since the signal is tapped on ground on the data line. This is particularly undesirable for measurements during system operation and must be avoided. Connecting the reference potential to the data line would result in a communication breakdown. However, you can avoid this by measuring both signals separately, and then indicate the signal difference. In this case potential separation of the two channels is not required. However, proceed very carefully in this case. There is a risk of short circuit if you connect the measurement cable incorrectly. Alternatively, you can use a differential probe. Another useful function is a multimeter integrated in the oscilloscope. In this case you can save one device. Modern digital oscilloscopes offer an integrated RS-232 interface or a USB interface for connecting to the PC. Thus measurements performed can be saved and documented with the PC.
            Attached Files
            "The one who says it cannot be done should never interrupt the one who is doing it."

            Comment


              #7
              Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

              It would be interesting to look at the spec on the Scope. 100 MHz is not a lot of bandwidth. The scopes I use in the 1980's had 75Mhz bandwidth of course they were analog. They had as I remember a asynchronous setting on them. Does this scope calibrate alright? The old ones had a post to check calibration and adjust for a square wave. What it looks like what is the scope does one sweep OK, but on the next sweep it is not in-phaze.I haven't work on storage scopes since 1987, when I was a calibration technician and I only had that job as a filler until I moved. The thing I thought with a storage scope, one could capture and event for a number of pulses and the o-scope did not go back across the screen. So as you view the screen you can keep turn a knob down it time.

              Comment


                #8
                Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

                Yea the probes passed the scopes built in calibration test when I tried it yesterday.
                The waveform also looked good when I hooked it up to a AC>AC power adapter to just check the waveform in my apartment out of curiosity.
                I also tried some other PSU's and there where no problem with the waveform on those either.
                The scope isn't very fast though, I think it's quite old so maybe there was simply too much happening on the Profibus network for the scope to handle it?

                The specs I listed above that Profibus recommends seems to all be fulfilled by the scope I used:
                http://www2.tek.com/cmswpt/psdetails...13304&lc=ES-MX
                "The one who says it cannot be done should never interrupt the one who is doing it."

                Comment


                  #9
                  Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

                  some scopes are miss-sold and you have to divide the frequency by the number of active channels.

                  i wouldnt expect that from fluke - but who knows!

                  Comment


                    #10
                    Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

                    So I was reading a little on what you are doing. Bus transmission of automated devices. They say they send both power and transmission down the same line and they use 150 ohms twisted pairs. You are working with Profibus DP which goes up to 12Mbits/sec. Seems to me to be a interesting field. You must be into robotics.

                    Comment


                      #11
                      Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

                      Fluke got back to me, they said they dropped the Fluke 215C / 225C series with the Bus Test feature due to low demand, what a shame
                      I looked a little more at the new Fluke 125B but it does not even have isolated inputs so that makes me even less interested in it.
                      I've also looked at all major scope manufacturers but not found anyone else that offers similar functionality.

                      stj: the scope I used was a Tektronix TPS2012
                      keeney123: Profibus DP is really just an implementation of RS-485 for industrial use.
                      It's in a way extremely simple but due to how resilient it is against communication problem it ironically makes it quite hard to troubleshoot.
                      In the machines I service there are allot of devices connected on the Profibus chain and any device with a problem may cause other devices to give alarms, yet function fine on it's own.
                      That's because the device with the worst signal to noise ratio in a system like this will seize to function.
                      "The one who says it cannot be done should never interrupt the one who is doing it."

                      Comment


                        #12
                        Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

                        Supposedly the differential inputs cancel out the noise? It seems to me that the lack of standards could create a big problem. What I have read is some equipment manufacturer specifies the inverting and non inverting signals a D- and D+. Of course there is also the synchronous and a-synchronous transmissions and if the lines are not terminated correctly one would read noise as a signal. It reminds me of all the people in the world talking different languages. It is very hard to communicate if you don't know that language.

                        Comment


                          #13
                          Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

                          Played around with an analog Tektronix 2215 60Mhz scope today.
                          Must say it was a breeze to work with, it's only one year older than me so maybe that's why we got along!

                          This scope did not have any problems with the signal, however it is obvious that a ghost signal is there so I understand how a digital scope like I used before can get confused about what to trigger on.

                          Originally posted by keeney123 View Post
                          Supposedly the differential inputs cancel out the noise?
                          That would be the definition of RS-485 signaling like used by Profibus yes
                          Originally posted by keeney123 View Post
                          It seems to me that the lack of standards could create a big problem. What I have read is some equipment manufacturer specifies the inverting and non inverting signals a D- and D+. Of course there is also the synchronous and a-synchronous transmissions and if the lines are not terminated correctly one would read noise as a signal.
                          Profibus is a standard so not sure what you mean, a quite good one at that IMO.
                          Attached Files
                          "The one who says it cannot be done should never interrupt the one who is doing it."

                          Comment


                            #14
                            Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

                            What I have read is those standards are not followed by all manufacturers even though they connect on the same line.

                            Comment


                              #15
                              Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

                              Fluke really came through to me.
                              They offered me a Fluke 225C at a price impossible to beat because it had no battery and intermittent power connection.
                              It was an easy fix, the PCB mounted power connector had gone bad, I ordered a new one from Fluke, plus battery and it works a treat
                              However just like the digital Tektronix TPS2012 I posted about above I'm unable to trigger on the Profibus signal.
                              Will try a simpler Profibus system when I have the possibility and see if it's any different.
                              Because I noticed with my analog Tektronix 2215 that I got a much cleaner signal on that machine...
                              (See attached pictures compared to the previous analog ones).
                              Attached Files
                              Last edited by Per Hansson; 12-03-2016, 08:50 AM.
                              "The one who says it cannot be done should never interrupt the one who is doing it."

                              Comment


                                #16
                                Re: Successor to Fluke 225C scope or equivalent for Profibus signal analysis?

                                Originally posted by Per Hansson View Post
                                Fluke really came through to me.
                                They offered me a Fluke 225C at a price impossible to beat because it had no battery and intermittent power connection.
                                It was an easy fix, the PCB mounted power connector had gone bad, I ordered a new one from Fluke, plus battery and it works a treat
                                However just like the digital Tektronix TPS2012 I posted about above I'm unable to trigger on the Profibus signal.
                                Will try a simpler Profibus system when I have the possibility and see if it's any different.
                                Because I noticed with my analog Tektronix 2215 that I got a much cleaner signal on that machine...
                                (See attached pictures compared to the previous analog ones).
                                Glad to hear they treat you good.

                                Comment

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