Hi all,
I’m working in Ban chat hydropower. I use data logger CR1000 to data acquisition dam monitor.
I connect network between 3 CR1000 and control room. I use MD485 connect multidrop bus RS485, use Rs232 connect to computer, CS I/O connect between CR1000 and Md485. I use Laptop I connected and collect data success, when I use PC, I still connect success, but cannot collect data from CR1000 and have warning
“Invalid low voltage signature, pack bus framing error”
“Transaction time out”
P/s: PC and laptop I use same window 7.
You can have me, give me some ideas to solutions my problem.
Thanks and best regards!
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Measurement and Control Equipment Co., Ltd(MC&TT Co., Ltd)
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So are you connecting both the PC and the laptop to the RS-232 port of the MD485 or are you using the laptop to communicate with the stations while bypassing the RS-485 link? I suspect that this is the latter.
The low level signature error produced in the LoggerNet comms log indicates that the signature nullifier used to validate message contents has flagged an error. There are typically two reasons why this happens:
- Fragments of the message are getting dropped on the link so the received message is missing data.
- Data is getting inserted on the link. This could happen if packets from multiple stations are getting mixed together in the base MD485 input buffer.
Possible solutions include the following:
- make sure that the MDROP protocol is enabled on all of the MD485 devices on the network.
- decrease the max packet size in both LoggerNet and in the datalogger settings. This will reduce the probability of data getting mixed and/or dropped.
- Slow down the RS-485 baud rate on all of the MD485 devices. Depending on cable length, termination, and operating environment, the faster baud rates may cause problems.
Thanks sir
I tried on suggesting of you but not effectively. I decrease max packet size from 1000 to 500 but computer not collection data success. Still happening error same:
“packbus framing error, invalid low level signature”
“Transaction failure, time out”
I use topology same picture please see the attachment.
http://upnhanh.mobi/f/zQBPIv
Length cable from CR at position the furthest to control room about 400m to500m. I only connect peer to peer one CR to PC for collection data.
Baud rate is used 19200. I changed some difference value but not success. Only baud rate (19200) sometimes I could collection data successful.
CR is instanced in corridor of dam.
One problem make me worry, RS485 I don’t connect grounding cable. You think it affect to effect?
This post is under review.