I don't use an external supply, just wire it as shown. Some RS-232/USB do not use the full +-12V swing and so may require your solution. But wire it correctly first and try it. I use the NI PCIe 8 channel RS-232 and it works fine. Some USB/RS232 only use 5V which does not work with everything.
FYI. I reversed engineered the serial port on an Instek PSP-603 power supply. It is complete luck if it communicates with another device. The optically isolated interface does not even come close to meeting the RS-232 specification for signal levels or drive strength. This is with the +12VDC provided on pin 4 which is very non-standard. Attached to this post is a pdf with the relevant serial I/O schematic. Many serial ports will successfully drive the photodiode in the supplies input but the supplies output circuit is badly out of spec. This explains why most people find they can transit to the supply but not get anything back. Shame on Instek for calling this an RS-232 interface.
i'm also facing same problem. please provide wiring diagram with adopter +12 volt of adopter is connected to pin 4 but ground of adopter???????
I had the same problem. The answer is hinted at in the manual where it says pin 4 must be high. That is the DTR pin. There is no need to use a remote power supply or any wiring to pull it high. Simply set DTR high in your software.
For example, I am using 'Termite', a very simple RS232 terminal. One of the communication options is "DTR/DTS" flow control. Once that is set, everything works fine.
Hope this helps.
- Carl Dreher
PS - Can you believe how awful the manuals are? Full of translation errors! You'd think a they could hire someone who lives in the destination country to edit it. And even more ridiculous, when their demo software starts, it has a spelling mistake in big print. "Connectting..."
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I have programmable power supply Chroma Model 62012P-40-120. I write RS232 communication based on the protocol from the manufacturer to set volatge ,current to the supply and measure the volatge and current output from the power supply. I have no problem with the communication . i can set the volatge and the current to the power supply and i can remotelly control (ON/OFF) the DC ouput of the supply. But when i try request volatge and current output of the power supply and connect them in series i can read the measure output either the volatge or the current but not both.
if the measure volatge request is 1st i can read it but no the current request and vise versa. But i can see the volatge and current ouput in the screen of the Power supply. Here i have attached the screent shoots of my labview programs. The status message is OK in both cases.