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logarithmic values displayed and charted

Posted: Thu Sep 14, 2017 9:00 am
by RickTCP
I am wondering if there are any suggestions as to how to display and trend chart logarithmic values.
I wasn't sure which section to post this question under.

We are reading 3x vacuum gauges. They are 0-10Vdc analogue signals, reading through ModbusTCP the raw values are 0 to 4096.
We need them to read from 1.00e-4 to 1.00e3

I have found the display value properties %1.2g but am still not getting the result required.
I am not sure I have the scaling set correctly, maybe the number of decimal places and scaling to use decimal places?

Any other thoughts please?
Thank you

Rick

Re: logarithmic values displayed and charted

Posted: Wed Sep 20, 2017 7:29 am
by RickTCP
More detail

W-NET/S-USB+ (64 tag) purchased in February 2017. Display logarithmic values with correct scaling.

This project has been held up due to physical site holdups. We are only now getting back to final configuration and testing.
One aspect causing problems is how to display values from a vacuum sensor correctly.

On the factory setup we have an Edwards Vacuum controller giving 0 to 10Vdc output (2V = 0.00001, 9V = 1000).
This is connected to a ModbusTCP input module giving 0 to 4096 counts for 0 to 10Vdc input.
I am having trouble trying to get this to display converted values correctly. I don't know if I am setting the Numeric Gate settings correctly?

I am simulating this in my office (not at the factory) and am using a licenced copy of WinLog Lite. I am using a different ModbusTCP input device in my office giving me 0 to 1000 counts for 0 to 10Vdc input.
To try to keep things simple I have only 1x input and am using an "Edit" object in the "Template" to view displayed values.

If I set Numeric Gate properties:
Value
Min value = 0, Max value = 1000, Start value = 0, Decimal digits, specified by a fixed value = 0
Conversion
Measured val 1 = 0, Engineering val 1 = 0, Measured val 2 = 1000, Engineering val 2 = 1000
The displayed values show as expected.

If I change Gate properties:
Value
Decimal digits, specified by a fixed value = 1
Conversion Engineering val 1 = 0.1
and tick - Apply decimal digits conversion.
The displayed values still show as expected.

If I change Gate properties:
Value
Decimal digits, specified by a fixed value = 2
Conversion Engineering val 1 = 0.01
and tick - Apply decimal digits conversion.
The displayed values start at the bottom as expected but now only go to a maximum display of 99.99.
I didn't change the Engineering val 2, it is still 1000.

If I change Gate properties:
Conversion - Engineering val 2 = 10000
The displayed value doesn't use the second decimal place, but now displays a maximum value of 999.9

For this application I need a minimum value of 0.00001 and a maximum value of 1000. This is 5 decimal places to the right of the decimal point and 3 to the left of the decimal point.
It seems to me there is a limit of 2 decimal places to the right of the decimal point and 2 to the left of the decimal point, or 1 and 3.

Is there some setting somewhere that will let me change this?
Can we use some calculation in script to achieve what is needed?

The next problem is trying to use a "Gauge" object in template.
It won't accept decimal point value as the low scale value. It initially accepts it, but when you try to reopen the Template builder it gives an error and locks up the computer. The only option I have found is to delete the Template and start again.

Will this be the same if we try to use a trend chart and try to have it plot down to 0.00001?

Thank you

Re: logarithmic values displayed and charted

Posted: Wed Sep 20, 2017 1:26 pm
by Isakovic
Hello Rick,

I'm not sure I get this right, is the scaling for your sensor linear or not? If not it shouldn't be much work to write a function for scaling if you know the formula for dependency of raw 0-10V value to measured value.

Do you know the type of sensor you are using? Do you have a spec sheet for it?