Analogue Input

1) Do you have PLC?:^) If yes - what PLC is it?

2) What sensor type do you use and how it's connected to PLC

3) Same questions on keypad

To be continued)))

Ok, lets start from the beginning:^)

Sensor. Generally it can see 3 ways of sensor measurements:

1) Sensor producing some standart signal (4-20mA, +-10V or whatever). Then you connect such sensor to AI module of PLC according to wiring scheme. Ensure, that input on this module is correctly configured (HWKonfig) and 4-position switch on the side of module is set properly (if present). Then you get code from ADC, where 0 corresponds lower limit (4mA for ex.) and 27648 corresponds to higher limit (20mA). So you can get signal value out of code. Then according to sensor documentation. You can use FC105 SCALE in this case.

2) Sensor is Siemens weighting cell. Then you connect it to SIWAREX module according to documentation, parametrize SIWAREX module (for ex. via HWKonfig), set zero (and also perform all other startup operations) and weight as REAL value

3) You get value from some abstract system via communication lines. Here everything depends on how it's connected to your system.

Keypad

1) Keypad can be BCD-keypad connected as multiple DI signals. In this case read DI by byte or word and use BCD-conversion instructions.

2) Keypad can be on HMI. In this case it would store tag value (entered weight) in some memory area of PLC - you just have to read it them

Comparasion

Well, doesnt worth extra tips - just read documentation (built-in Step7 by F1 key) :^) General rule - you can compare variables only if their type match (so you can't compare INT with REAL - should make them of one type beforehand).