EBME Forums Forums Maintenance Test Equipment About Timeter RT-200

Added VCC and GND definitions for U12 and U9

schematic diagram

About "zeroing" and "drift" ... Section F of the March 1988 manual talks about this.

Meanwhile the Troubleshooting Section informs that "excessive drift" shall generate a "HELP 0" display; so if no such message is evident, hopefully we can assume that all is well. There are, however, some pots that may be tweaked if you insist!

Unfortunately, my RT-200 RT-203 flow module is faulty.
The fault phenomenon is that the screen displays "HELP 0".Press "30" to enter the V/F converter and see that the data is continuously decreasing.Use a digital multimeter to measure A3A3A1 (HI, LO voltage values),It is a constantly changing value, not 0 +/-.005VDC.

I tried adjusting A3A3A2 R1102?Try to keep the V/F converter in the range of (250-500),HI-LO voltage maintained at 0 +/-.005VDC?

But after restarting, it immediately displays "HELP 0",The V/F converter shows a value of about 710 and keeps decreasing.Only when the V/F converter display value is in the range of (250-500) ,After entering the function code, it can be displayed normally and "reset to zero" normally.But this state won't last long,When the V/F converter is lower than 250, "HELP 0" appears again


I removed the pressure sensor from the RT-203 module PCB,Use 4 4K ohm fixed resistors to form a Wheatstone bridge,Reconnect the sensor socket,The V/F converter display value is stable, and the HI-LO value is also stable.

Final pressure sensor thermal stability failure, possibly due to aging.

If anyone knows a compatible sensor model or the data sheet of the original sensor, And the calibration method after replacing the pressure sensor?please let me know. I would be very grateful.Thanks










test video

In the process, I discovered a mysterious resistor network "1698-99-0"

I drew the circuit schematic.
If anyone can understand it,And know the meaning of R1109 (TC), R1102 (NULL), R1104 (XD BAL), R1116 (ZERO), R1123 (VB SET), please tell me,Thanks.

Hallo everyone.
I found the model number of this pressure sensor, it is "125PC05D1", and found the data sheet, unfortunately it has been discontinued and I have not yet found a replacement model for it

Hello, here is offer at ebay

https://www.ebay.com/itm/153522618703

Thanks.

I understand, but I am in a country where I cannot buy from EBAY or the shipping cost is much higher than the price of the pressure sensor itself.
So I can only look for another model to replace it.