Hello everyone,
I've set up Clampex 10.5 for an Axopatch 200B connected to a 1550A Digidata and I have this problem: the gain on Clampex is changing randomly. This happens both while recording (e.g. three sweeps at gain 1, than one at gain 5, back to 1 and then two sweeps at gain 0.1) and without any protocol running. Of course this oscillation causes the Y-axis to change its scale continuously.
Clampex itself, however, is still responsive to any change in the gain I apply from the output gain knob on the amplifier. I can set it to whichever value and Clampex follows correctly. But then it starts to oscillate again between 0.1, 1 and 5...
I have also changed the BNC cable connected to the gain but the problem remains...
Anyone had this problem before? Is there something I'm missing here?
Many thanks!
(note: all telegraphed connections, signals and scale factors set are correctly).
Hi Dario,
Do you know if the problem comes from your amplifier? If no, then try to see if the gain is telegraphed properly and does it change due to increase/decrease of signal size. I mean, does the gain increase from bath mode to cell attached mode. You can test that with a model cell as well.
Regards,
Debanjan
Hi, from your wordings, its pretty much clear that the telegraph inputs are not connected properly. The telegraph inputs 0, 1 and 2 Should be connected to Gain, Frequency and Capacitance of the amplifier (back side) and you should check the same in the software. It does not matter whether you connect the capacitance or not. Once you do this, you can observe that the scale in the axis changes as you change the gain but the current level remains the same.
You may want to look at your gain telegraph signal on an oscilloscope or a digitizer input channel. Sounds like you may be picking up noise that randomly pushes the telegraph signal across the threshold between two gains.
I am sure you are aware that Clampex does not support switching the gain in the middle of the acquisition. Gain scaling is applied at the beginning of a protocol, and if you you switch the gain during protocol acquisition, scaling from then on is incorrect.
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