| ??? 09/07/10 11:29 Read: times |
#178465 - Trial Successful ! :) Responding to: ???'s previous message |
Hello all,
I tried it with PWM. Michael, The application note an107 was very helpful for me :) I used 16 bit PWM-->Opto-coupler-->Low Pass Filter-->Op-amp buffer-->mV oputput. Found the results of simulation as follows. PWM Value[HEX]--Duty cycle %--Output [mV] 000F--------99.98--------2340- Fluctuation 1000--------93.75--------2220 2000--------87.50--------2080 3000--------81.25--------1936 4000--------75.00--------1790 5000--------68.75--------1643 6000--------62.50--------1497 7000--------56.25--------1349 8000--------50.00--------1202 9000--------43.75--------1055 A000--------37.50--------908 B000--------31.25--------760 C000--------25.00--------612 D000--------18.75--------464 E000--------12.50--------315 F000--------6.25---------168 FFF0--------0.02--------14+ fluctuation The results are very linear with PWM value 0x1000 to 0xF000. [However the mV output was fluctuating at PWM value 000F and FFF0 ]. The linear middle band is sufficient for me for 4-20mA conversion. I can now simply convert 2220mV to 22.20 mA and 315mV to 3.15mA. Thanks to all of you for giving your time for guiding me :) Anita |
