ICP DAS USA 7000 user manual

It is recommended to use the “trial and error” rule. The trial and error rules are given as follows:

(1)If the length of RS-485 is about 1.2 Km, try 120Ω first

(2)Run TEST.EXE of NAP7000S

Select function_5, run continuously for at least 8 hours to make sure communication is OK.

(3)If function_5 finds many communication errors, use an oscilloscope to check the waveform. The waveform will tell you

whether the terminator is too small or too big. Then adjust your terminator and run TEST.EXE again.

(4)

(5)If the correct terminators are found, run the TEST.EXE continuously for at least 8 hours to make sure there are no communication errors.

The function_5 of TEST.EXE, given in NAP7000S, will automatically read “testing command” from TEST.DAT and continuously perform “send- receive-testing”. It will continuously test and record all testing results. Therefore this function is especially designed for RS-485 network stability

evaluation. If you run this function_5 continuously for 8 hours and find no

check errors, this means that your RS-485 network is very stable. Also

this means that your terminators match well now.

NOTE 1: The value of the terminator depends on the RS-485 wire used. If the RS-485 path is very long, don’t use a cheaper wire. It is recommended to select a high quality wire such as the Belden 1583A.

NOTE 2: The terminator is different for various applications. Therefore we can’t provide a terminator with the 7520 or the 7510. The user must choose the correct terminator by them self. It is recommended

to use a carbon, 1/4w resistor.

7000 Bus Converter User Manual (version 1.2,Feb/2003, 7PH-006-10) --------------- 76