two gpib instruments not found but one can

[Lee1830]

Several days ago,I could not find any instrument.But today I opened the computer and then powered on the instrument(lock-in amplifier),and pressed the interface setup key to display on GPIB, the address is 8.And I used MAX to scan for instruments, and then I found instrument0, VIs also can be executed.

I actually did the same thing as I did before.And then I want to communicate with another instrument at the same time.So I powered on the monochromator(MS257) and pressed the rem key to lease control to the computer.Then I clicked scan for instruments again, I cannot find anything and I lost instrument0.I tried several times,also tried to only power on the monochromator, the result is not found always.

The gpibboard0 is at address 0.Instrument0 is at address 8.The default address of the monochromator is 6 but I am not 100% sure that it is at address 6.

Can anyone give any idea?Because I don't know what's the problem and I can not check or set the address of the monochromator(MS257).

[Lee1830]

how to change the two interfaces when doing a VI related to two instruments

[smercurio_fc]

You said you tried to power on only the monochromator. Was it connected on the GPIB bus at the same time as the lock-in amplifier? Did you try connecting only the monochromator to the computer? Did you try swapping cables? Did you try other cables? How do you have the GPIB cables connected? Do you have the manual for the monochromator? It will tell you how to set the GPIB address.

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@Lee1830 wrote:
how to change the two interfaces when doing a VI related to two instruments

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I have no idea what you are asking here.

[Lee1830]

I have tried to use another cable and power on the monochromator only,but it still doesn't work.

The address of the monochromator is said to to be set by using the dip switches on block U12 on the IEEE-488 interface board,the factory default address is 6.I actually don't quite understand what is the manual trying to say.Should I take off my PCI-GPIB card and find the U12 to change the address?What if the address is just 6?

Another question is that Iam using one PCi-GPIB card to communicate with two instruments,so there are two cables,shouldn't I consider the selecting the interface before running the program?e.g. after I send a command to one instrument, I should wait for execution,and then change to another interface to read the data of another instrument,is that right?

[Lee1830]

what do you mean by how did I connect the gpib cables?I first connect the pci-gpib card and the lock-in amplifier with one cable, and then I use one end of  another cable to plug into the former cable on the pci-gpib card,and the other end connecting to the monochromator,is this not correct?

[Lee1830]

I also used ICBC to find listeners from address 0 to 30, but I can find nothing

[Lee1830]

I couldn't understand why that I was doing right with the lock-in amplifier,but once I power on the monochromator and scan for instruments,then no instruments found why I would lost the lock-in amplifier?

[smercurio_fc]

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@Lee1830 wrote:

I have tried to use another cable and power on the monochromator only,but it still doesn't work.

The address of the monochromator is said to to be set by using the dip switches on block U12 on the IEEE-488 interface board,the factory default address is 6.I actually don't quite understand what is the manual trying to say.Should I take off my PCI-GPIB card and find the U12 to change the address?What if the address is just 6?

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No, you do not set the address of the instrument on the GPIB controller. That makes no sense. The address of the instrument is set at the instrument. The address of the controller should be 0 if you have just one. If you have 2 controllers then the first would be 0 and the second would be 1.

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Another question is that Iam using one PCi-GPIB card to communicate with two instruments,so there are two cables,shouldn't I consider the selecting the interface before running the program?e.g. after I send a command to one instrument, I should wait for execution,and then change to another interface to read the data of another instrument,is that right?

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You're using the term "interface" quite loosely, and I have no idea what you are referring to. You have only one "interface": GPIB. You have 2 instruments. If you send a command to one instrument you can then send a command to the other instrument. You would not need to wait for the other instrument to respond unless the command you send to the second instrument is dependent on the value you are returned from the first. One thing you cannot do is send commands simultaneously, since GPIB does not allow that.

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what do you mean by how did I connect the gpib cables?I first connect the pci-gpib card and the lock-in amplifier with one cable, and then I use one end of  another cable to plug into the former cable on the pci-gpib card,and the other end connecting to the monochromator,is this not correct?

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GPIB cables can be connected in daisy-chain fashion (controller -> instrument 1 -> instrument 2 -> etc), or in star fashion (instrument 2 <- controller -> instrument 1).

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I have tried to use another cable and power on the monochromator only,but it still doesn't work.

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I couldn't understand why that I was doing right with the lock-in amplifier,but once I power on the monochromator and scan for instruments,then no instruments found why I would lost the lock-in amplifier?

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I didn't say to power on the monochromator only. I said to have only the monochromator connected to the GPIB controller. One cable. Controller -> monochromator. Does this work? If not, this indicates that either the monochromator's GPIB interface is broken (which is a possibility here), or it requires a special configuration of the controller, or it is not compatible with the GPIB card you have.

[JÞB]

From what you are describing there are several possibilities:

• both instruments are assigned address 8- (they would both try to respond and no communications would be done so you would lose both instruments in MAX)
• the monochromator GPIB interface is bad in some manner that breaks the handshaking lines of the GPIB bus (the entire bus would be brought down and all devices would dissapear from MAX)
• One of the GPIB cables is damaged in some manner that breaks the handshaking lines of the GPIB bus (the entire bus would be brought down and all devices would dissapear from MAX)

Severio's methodologoy (attach only the monochromator to the GPIB bus using a known good cable) will isolate which case(s) are present in your system.

[Lee1830]

Thank you,I have tried to connect the monochromator with the PC only using a good cable.So it should be the monochromator's problem.