Every PLC and HMI tutorial on plctr.com: project setup, ladder and structured text, communication, troubleshooting and commissioning, written from the plant floor.
1200 tags collected once a second is 160,704,000 values a day, and at the 12 bytes a historian typically spends on a timestamp, a value and a status that is 1.93 GB a day and 704 GB a year. The same 1200 tags, with a deadband at the collector and a compression test at the … Read more
LIM and MEQ: Testing a Value Against a Window, and Against a Mask A LIM with a Low Limit of 4000 and a High Limit of 20000 passes the rung while a 4-20 mA input is in range. Type the same two numbers into the opposite fields and the instruction passes the rung for exactly … Read more
CTU, CTD and RES: The Count That Keeps Going Past the Preset buffer_count.ACC reads 41,206 against a preset of 500, and .DN has been true since some time on Tuesday. The line is running normally, the zone-full interlock has not released since then, and nobody can find the fault because there is not one. A … Read more
One firewall rule is usually all a plant data project asks for: TCP 1433 outbound, from a gateway at 192.168.1.40 on the cell network to a SQL Server at 10.20.4.16 on the business network. That rule gets refused, and the refusal is right. What gets approved instead is a broker sitting in a demilitarised zone … Read more
BTD: Pulling a Field of Bits Out of One Word and Into Another The status DINT coming back from the bench scale reads 306,997. The weight is 1,199, and the rest of that number is a units code, a stable flag and a sequence counter, packed into the same word because the vendor had thirty-two … Read more
MOV, MVM and CLR: Moving a Word, and Moving Only Some of Its Bits MOV a DINT holding 123456 into an INT tag and the INT reads -7616. No fault light, no message, the rung stays exactly as green as it was, and the only record that anything was lost is S:V, which nobody has … Read more
When an Axis Will Not Enable: the Six Gates MSO Has to Pass Before Anything Moves The MSO rung goes true on a 2198-D032-ERS3 axis, MSO_1.EN sets, and then nothing happens: no .DN, no .ER, no error code to look up, and the machine sits there. Axis_01.AxisState reads 5. Five is Inhibited, and a start … Read more
An Edge Gateway That Buffers: Six Hours Offline, and Then What Six hours of the carton transfer at its real change rates is 2.12 MB. Four machines on the same gateway is 8.49 MB. The same four machines with every tag published every second and no deadband on anything is 31.66 MB, and that is … Read more
The Feedback Fault That Is Not the Encoder: FLT S45, the DSL Cable and the Ground That Hides It A 2198-D020-ERS3 running a VPL-B1306F has thrown FLT S45 – FDBK COMM FL four times in six weeks, and there is a third motor on order. The drive has been measuring the actual cause the entire … Read more
Position Error and Following Error on a Kinetix Axis: What a Trend Says That FLT S54 Does Not A 2198-D020-ERS3 threw FLT S54 – POSN ERROR at 14:02 and again at 14:19, and the fault-code spreadsheet describes it in one sentence: the position error of the position control loop exceeded Position Error Tolerance for longer … Read more
Axis Faults on a Logix Motion Axis: What AxisFault, MotionFault and the Attributes Are Telling You On a 1756-L83E, Axis_01.AxisFault reads 1, Axis_01.MotionFault reads 0, and the 2198-D032-ERS3 in the panel is showing FLT S54 – POSN ERROR. Somebody will now spend twenty minutes looking for a motion fault that does not exist, because the … Read more
Sparkplug B Properly: Birth and Death Certificates, Metrics and Rebirth The first message the carton transfer gateway sends is 592 bytes on the topic spBv1.0/Plant2_CartonLine/NBIRTH/GW-TR14, it carries all 19 metrics the node will ever publish, and it goes out at QoS 0 with the retain flag clear. Everything about that sentence looks wrong to somebody … Read more