Hii I am facing some problem while interfacing CS5534 ADC. I am using this for a load cell application.The following are the connection specfication.
1. +Va and +Vref are shorted and connected to a +2.5V (tolarance of +/-5%) 2. -Va and -Vref are shorted and connected to a -2.5V (tolarance of +/-5%) 3. +Vdd is connected to +5V 4. Load cell excitation is +/- 5V 5. Input to the ADC is given through an instrumentaion amplifier (AD620-Analog devices) in the range of +/- 2.5V single end out 6. all grounds are shorted together
I am usng only one channel of the ADC(CHANNEL-1) of four avalibale chanels .All the other 3 channels are shortd and grounded.Gain is 1. Not using internal amplifier
software specifications:
All the initialisation process are done as per the datasheet. Conversion speed is 60 samples/sec(i tested withe diffrent speed) A0 and A1(analog output ??) pins on this IC are kept open since it is not required for my applications)
Now my readings are okay,i mean even the fluctuations are managable. I am facing the following 2 problems
1. adc is in continuous mode,and the readings are okay. when i reset readings are same. But if i keep the system off(power supply off) for long time(more than 30 mins) and then if i make it ON, the readings of the adc is changing.it is becoming some higher values,approximately some +30 counts more from previous reading., and then the readng will be slowly decreased and come to the normal original value(this decreasing time is even more than 45 mins!!!).this is happening only if i keep the system off for a long time period, and there is no problem if i immediatley do a system off-on. the voltage on the power supply is verymuch stable through out at all the condition.
2. In this scenario, i connected 8 load cells through a multiplexer(using only one load cell) ,i am not able reading properly(able to get the values properly if i flush out 2 readings each time before taking the reading ),this slows down the total process and the total system becoming too slow. this problem comes in picture only if i use the ADC conversion in continuous mode
I would really appreciate your help on this.My main concern is with the first scenario(problem no.1) please let me know if you need any more software or hardware specification.
Thanks in advance
Faslu Rahman and Govind Bangalore-INDIA