Voltage measurement (OCP, open circuit potential) using the AD5940 resp. ADuCM355

Hi,

AD5940 is similar with ADuCM355, the difference is ADuCM355 has a cortex-m3 MCU inside.

1. You need to set MUXP and MUXN to the differential voltage you want to measure. For example, set MUXP to pin CE0 and MUXN to SE0 to measure the voltage between CE0 and SE0.

2. There is no input impedance parameter in datasheet, but has a input current. Please check Table 1, ADC INPUT section.

Regards,

Neo

Hi,

AD5940 is similar with ADuCM355, the difference is ADuCM355 has a cortex-m3 MCU inside.

1. You need to set MUXP and MUXN to the differential voltage you want to measure. For example, set MUXP to pin CE0 and MUXN to SE0 to measure the voltage between CE0 and SE0.

2. There is no input impedance parameter in datasheet, but has a input current. Please check Table 1, ADC INPUT section.

Regards,

Neo

Hello,

I am also interested to perform an OCP with the AD5940. In the documentation, there is no SE0 available from MUXN. According to the documentation, MUXN can be configured through the register ADCCON, bits [12:8] (MUXSELN). Here is an extract of page 61 / 134 (Rev C).

The MUXSELP can be connected to any of pins RE0, CE0, SE0, DE0 though.

Is there any way to measure potential between SE0 end RE0?

Thank you.

Best regards,

Hi,

There are many ways to measure voltage across SE0 and RE0.

One way:-

1) Connect the two terminals of your load to AIN2 and IN3 respectively and measure the voltage across them,

AD5940_ADCMuxCfgS(ADCMUXP_AIN3, ADCMUXN_AIN2);

AD5940_AFECtrlS(AFECTRL_ADCPWR|AFECTRL_SINC2NOTCH, bTRUE);
AD5940_Delay10us(16*25);
AD5940_AFECtrlS(AFECTRL_ADCCNV, bTRUE); /* Start ADC convert*/
AD5940_Delay10us(WaitClks);

while (!(AD5940_INTCTestFlag(AFEINTC_1, AFEINTSRC_SINC2RDY)));

AD5940_INTCClrFlag(AFEINTSRC_SINC2RDY);
afeResult = AD5940_ReadAfeResult(AFERESULT_SINC2);
AD5940_AFECtrlS(AFECTRL_ADCPWR|AFECTRL_ADCCNV|AFECTRL_SINC2NOTCH, bFALSE); /* Stop ADC */

measured_voltage = AD5940_ADCCode2Volt(afeResult&0xffff, ADCPGA_1, 1.82);

another way:

1) Measure voltage of SE0 w.r.t. VERO0, (AD5940_ADCMuxCfgS (ADCMUXP_VSE0 ,ADCMUXN_VZERO0);)

2)Measure voltage of RE0 w.r.t. VZERO0, (AD5940_ADCMuxCfgS (ADCMUXP_VRE0 ,ADCMUXN_VZERO0);)

3) Subtract (1) from (2).