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PWL not working as it should?

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PWL not working as it should?

Postby terrypin » Sat Jun 21, 2014 3:52 pm

I installed PSW with help from Tech Support yesterday and it's working OK.

Today I installed PWL, apparently successfully, but it seems to be faulty, or provoking a fault in the h/w unit itself. This occurs during the settings stage, regardless of whether or not any signal input is connected.

It's illustrated by this series of screenshots, in which I accept the defaults in setting up a new file. At stage 5, the unit starts audibly 'chattering', presumably an internal relay, and the LED simultaneously flashes.

Image

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Naturally this is a Saturday! So unless I discover the cause myself meanwhile (and I've been trying for several hours already), or I get a solution by email or in the forum, I will 'phone on Monday to discuss.

--
Terry, East Grinstead, UK
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Re: PWL not working as it should?

Postby Martyn » Sat Jun 21, 2014 6:04 pm

The 2204 & 2205 scopes have relays which switch between the high and low voltage ranges on each channel. When running in PicoLog, the input signal is fed through from one input connector to both channel’s A to D converters in parallel to get twice the bandwidth. Then the other input connector is routed through the same pair of A to D converters and so on in a cycle. At any one time, the unused input connector and pre-amplifier chain is set to the highest voltage (lowest gain) condition to avoid injecting cross-talk onto the live channel. If either channel is set to +/-1V or lower, then the gain relay will cycle continuously.
The way to have two channels in use without the relay noise is to have both set to any voltage greater than +/-1V (+/-2V to +/-20V, they can be different).
For the smaller voltage ranges less than +/-2V (+/-1V to +/-50mV) the clicking can be reduced or eliminated by increasing the scan time under the "Edit Measurements" section. You will need to do this for both channels.
This is inherent in the hardware design and cannot be changed or fixed in software.
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Re: PWL not working as it should?

Postby terrypin » Sun Jun 22, 2014 6:33 am

Thanks Martyn, much appreciate the weekend response. That would have been nagging me all day today!

I'll try those suggestions later today.

That design sounds like a surprisingly backward step compared to using Picolog with my old ADC 200/50? :(

--
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