You are looking at the RS-485-side of an RS-232/RS-485
converter and the power supply voltage for the converter is
+5V. Under idle conditions (no transmission), and assuming
you have enabled the RS-485 output: what would you expect
at:
(a) Output A measured against output B
(b) Output A measured against ground
(c) Output B measured against ground
Answer / carl_ellis
You are looking at the RS-485-side of an RS-232/RS-485
converter and the power supply voltage for the converter is
+5V. Under idle conditions (no transmission), and assuming
you have enabled the RS-485 output: what would you expect
at: (a) Output A measured against output B (b) Output A
measured against ground (c) Output B measured against ground
With a supply voltage of 5V, the sink driver is usually able
to pull the voltage on each conductor fairly close to signal
ground (0.5V), but the source driver usually has a voltage
drop of approximately 1-1.5V. The voltage swing on each
conductor is therefore typical 3-3.5V, but it may be as low
as approximately 2V.
Answer a)
Hence, output A (-) measured with respect to output B (+)
would read approx -3V to -3.5V ( a negative voltage) in the
idle state. (The logic is inverted: a negative voltage is a
mark or logic 1)
Answers b and c)
Output A (-) measured with respect to ground: ~3.5V to 4V
Output B (+) measured with respect to ground: ~0.5V to 1V
This is a 3V differential, with 2.5V Vcm common mode, where
common mode is the mean of the differential plus the Vcm
common mode above the reference ground.
Carl Ellis
Measure First
Is This Answer Correct ? | 3 Yes | 1 No |
Is SmartPlant Instrumentation taking advantage of the quality assurance procedures within Intergraph?
how to calibrate the radar transmitter for measuring the exact tank level if tank is having agitator moving continiously because due to agitator tank surface level will vary every time.
What is the difference between floating and fixed voltage?
i have an interview in Qatar Petroleum. So please provide the all details abt fire & gas systems
Why we used cage in control valve?
What is force balance principle? State some of its’ advantages.
Pressure tx shows 1 mbar but we need 1000 mbar at this process condition .. how can we sort it out .
what is plc? Basic function of plc? application of plc in industry? What is lader diagram ? What is the main advantage to use plc in industry?
How can we calibrate the level interface for Fisher® FIELDVUE® DLC3000?if use water to calibrate and our liquid SG are 0.75 and 1 ,Displacer height=14" and How much should be set SG in trasmitter during calibrate,for URV and LRV how shold be set
what is the difference between Digital output DO signals /Commands for start/stop and Solenoid valves ??
how we can calibrate level transmiiter in field?
Identify the electrical variable that is either directly or inferentially used by various instruments to determine the value of a measured variable.