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

what is difference between 1/2"NPT & M20 x 1.5 cable gland?

8 Answers  

---

Is there any temperature compenasation for the air flow from FD fan & SA fans which supplies air to the Boiler?

2 Answers  

---

what is the usage of QDV & VOLUME BOOSTER.

2 Answers   ADMA OPCO,

---

What is Cavitation?

2 Answers   Gujarat Borosil,

---

radial & axial vibration sensor output voltage is ac or dc volt?

8 Answers   Vedanta, Voltech,

---

hello dear i have faced problem in drum level transmitter. the problem is when i engrize the meter meter shows 100% but the actual level 40 or something plz suggest me

7 Answers  

---

Basically iam Instruemntation Engineer, but Iam interested in Instruments design engineering, so plz guide, is there any course, training or Softwres to become Instrument design engineer??.

0 Answers   Honeywell, Tata Steel Limited,

---

How to find the range of DP cell Transmitter for measurement of level in closed vessel.

3 Answers   Rosemount,

---

what is a good line as ic engineer as maintenance ,oc, project, calibration ,validation engineer?

0 Answers  

---

what is the field bus calble ? what are diffrences in orang colur cable and black coular calble ?

0 Answers   ABB, Yokogawa,

---

what is the input to be given digital temp controller during the the calibration time?

2 Answers  

---

can anyone can let me know in Eurotron Micro cal 2+ calibrator in milli amps source mode we are not able to get 20 milli amps output it only produces 1.52 milli amps out, but display shows increase in milli amps , and err6 displays, let me know how to remove the err 6.

0 Answers  

---