I am using a PCS500, connected to an IBM T43 laptop. It works well, and produces transient recorder files when requested.
My question concerns how to interpret them.
In the header of each file, there are entries like these:
TIME STEP:
10 = 0.1s
VOLTAGE STEP:
CH1: 32 = 5V
CH2: 32 = 5V
The table that follows has a column “N” (increments of 1), and two columns CH1 and CH2.
I am confused about how to convert the values for each channel to voltages.
For example, with a “voltage step” of 5V (selected on the transient recorder), the file reports a value of 135, and a multimeter across the same two points as the PCS shows 0.8 volts.
If “32 = 5V”, then 135 should equal 135/32=4.2 steps of 5 volts each, or 22.5 volts. But the only way to get the actual value of 0.8V is to DIVIDE 4.2 by 5, instead of multiplying it.
Is this the correct method to convert the PCS output to voltage? If so, can you explain why it makes sense? And if not, can you tell me how to do so?
As for the time step, am I correct to understand that if “10=0.1s”, then each unit in the N column equals 0.01s? It seems obvious, but you never know …
To add to the mystery, I found two output files, observing the same signals, which showed exactly the same CH1 and CH2 values, but one indicated a voltage step of 1.5V, and the other of 0.5V.
The behavior on the oscilloscope screen makes sense: when changing from 1.5V to 0.5V, the 1V signal moves, as it should, from 2/3 of a major unit to 2 major units. But the transient recorder output is unchanged.
The time step values are as you expected.
The voltage data is just the raw data without any ground reference.
The data is 00 if the trace is at the bottom of the screen.
The data is 255 if the trace is at the top of the screen.
In oscilloscope mode there are the ground (GND) levels in A/D converter counts included to the data file.
In the transient recorder mode you can select first coupling GND and run a short recording.
Save this file to check the GND reference for the next recording.
To calculate the absolute voltage you have to subtract the GND reference value from the recorded data.
Example:
GND reference: 128
VOLTAGE STEP: 32 = 5V
Recorded data point: 225
Voltage = (225-128)*5V/32 = 15.16V
[quote]The behavior on the oscilloscope screen makes sense: when changing from 1.5V to 0.5V, the 1V signal moves, as it should, from 2/3 of a major unit to 2 major units. But the transient recorder output is unchanged.[/quote] You have to make a new recording run with the new settings. The display does not “zoom” in vertical direction if you just change the Volts/Div setting.