Ashu@automation

How do you read out the IP address of the S7-300 CPU in the user program at run time? You call the "RDSYSST" instruction in order to read out the IP address of the S7-300 CPU in the user program. With the "RDSYSST" instruction you can read out a parts list or excerpt of a parts list of the system status lists (SSL or in German SZL). With the SSL ID and the INDEX you specify the parts list or excerpt of the parts list and the type or number of an object in a parts list. Use the SSL ID = 37 (hex) and the INDEX = 0 (hex) to read out the IP address of the S7-300 CPU. Fig. 01 Inputs and outputs of the "RDSYSST" instructions Table 01 shows the inputs of the "RDSYSST" instruction.   Parameter Data type Description REQ BOOL REQ=1: Trigger for processing SSL_ID WORD SSL_ID of the parts list or of the excerpt of the parts list SSL_ID=w#16#37: Read out of the IP address of the S7-300 CPU INDEX WORD Type or number of...

Analog module in Siemens convert voltage (or other) into integer 16-bit (word data type), so it have 2^16 = 65536 count. Analog module in Siemens comes with varies bit-resolution 8-15 . So for max count (15 bit) it have 2^15=32768 count (0...32767).  PLC always convert voltage (or other) into word value regardless the resolution and its conversion is shown below:   Volt:    0....10         into Count: 0.....27648 although the rated range is 0-10V (0-27648), PLC also have over-control range (27649-32511), and overflow (32767). Noted that 27648 is not analog maximum value, its the analog rated maximum value. The real maximum value is 32767 (overflow) -> 2^15. So if you give module's input 10.2V it will convert into value bigger than 27648 and not destruct the module (as long as it still below permissible input voltage). But i still don't know why Siemens choose 27648 not 27000 or other (maybe rated range 84...

DIFFERENCE BETWEEN THERMOCOUPLE AND RTD The most notable difference between a thermocouple and an RTD (Resistance Temperature Detector) is the principle of operation.   A thermocouple operates on the principle that two dissimilar metals joined together will produce a voltage related to a temperature difference. An RTD operates on the principle that electrical resistance of certain metals changes in a predictable way depending on the rise or fall in temperature. Advantages of the thermocouple include a wide temperature measuring range (depending on the thermocouple type the range can be as much as from -300°F to 2300°F), fast response time (under a second in some cases), low initial cost, and durability. Overall, thermocouples are able to withstand rugged applications.    Advantages for RTDs include stable output over a long period of time, ease of recalibration, and accurate readings over narrow temperature spans. Disadvantages, when compared...