Posts Tagged serial communications
Everyone agrees that it’s good practice to keep a record of configurations and setups for any field instrument. I’m constantly recommending it to our customers for their transmitters, controllers, recorders, and other complex configurable devices.
Siemens clamp-on ultrasonic flowmeters even have a system in place to make this process easy. By connecting the meter to a PC through the RS-232 serial port, you can use a terminal program and the SITE command to fetch a data file that holds all the instrument’s configuration data.
The terminal program can also be used — with a set of instructions specific to the flowmeter — for viewing real-time operational data, performing device setup, uploading logger data, or uploading configurations known as SITE setups.
Recently, I was called to visit a plant and look at a misbehaving flowmeter. From previous discussions with the operator, I knew he’d saved SITE setup files for every flowmeter installed in the plant.
I asked if the customer would e-mail me the setup file before my visit, so I could check out how the flowmeter was set up. My request was met with a chuckle and “Well, if you really think it’s worth it…”
Sometimes I get lazy and don’t follow my own rules. (Rule #1: Test EVERYTHING!) That one oversight cost me three hours when I could have solved a problem in three minutes. Maybe you can learn from my mistake.
The goof happened at a customer site last week. He had a Siemens MultiRanger 100 ultrasonic level transceiver, and was trying to connect to it via Modbus using Siemens SIMATIC PDM software on his Windows XP laptop PC.
Early on, the Lesman salesman who worked with this customer had connected to the MultiRanger from his laptop using PDM, but only one upload worked successfully. The rest failed. The salesman had lent the customer his “known good” serial cable that he’d used for the successful upload.
Siemens tech support had offered the customer several “Try This/Try That” suggestions, but came to the conclusion that a software program on the customers’ laptop had locked up the laptop’s internal serial port so PDM couldn’t access it. The customer’s IT guy ran a port scan program, but could find on application or service running on COM1. Plus, they’d used the serial port successfully for other connections.
I couldn’t do anything more for the customer over the phone, so I grabbed my serial comms toolkit and headed to the site myself.