hi

help me please

i am about to control a chamber temperature 0-400 C precisely with logo! 8---12/24 RCE+K type thermocouple and a 0-10 VDC converter.i made all connections but i have problem whit analog input scale and analog settings.please help me to set a program to control temperature.

i need to control the temperature in 24 steps and smothly to prevent post heating.it is required to contorl the temperature in ON/OFF method not PI method.

thanks a lot for your help.

thnaks a lot for your answer

but there is 3 more problems:

1:the temperature reading digits keeps changing upper and lower digit,due to this changes the out put relay connected to logo!8 output 1,keeps closing and opening its contacts and when the temperature is at ON threshold, causes my output (torch) to turn on/off very rapidly and this can blow my torch away.

how do i get a stable reading...and smooth output...?

2:the temperature reads my place 46.4,while the temperature in my place is about 28 C.

how do i correct this issue?

3:temperature rise is very rapid.

how can i limit the temperature rise, and prevent the rapid change of the temperature near the set points

Any help would be appreciated!

hi

1:the logo and 0-10v trensmitter are side by side and connection is not shielded,but the wire has only 10 cm length.thermocouple wire is 6 meters and shielded.

2:hystersis?how to set a hystersis in logo?

3:download and run your program

is it possible to faulty transmitter?????

hi

i did some other checks on the circuit and i think the thermocouple is not working properly.

1:i removed the thermocouple(K type) and put the tip in the boiling water and i measured the mV using a precision multimeter (sanwa pc 5000),at the boiling water the milivolt was only 2.68 milivolt,but mV of boiling water must be 4.096 mV(from the OMEGA table).then put the tip in the glass of ice+water ,it was  -1.268 mV- i checked the number in table,it was for  -25 celsius-and my freezer is only -17 celsius.also the ambient temperature measured with this device is only 0.8 celsius and boiling water measured only 28 celsius.

2:and i measured the resistance of the device too.it was 1.94 ohm.but i did not get any useful info about thermocouple resistance test.

is the thermocouple bad?

is the resistance bad?

and if possible send program with higher resolution for 0-10V and 0-400 celsius if available.

thanks you for your help.

i need a program to control 0-400 celsius with logo 12/24 rce and a K  type thermocouple and a 0-10 v transmitter-i need to do control in several temperature steps and in 0.25 resolution.

any help wolud be appriciated....