ADS1018: Suitable ADC required to monitor 3-phase AC Load Using Current Transformer

Hi Angel,

Thank you for your suggestion.

1. In some applications, Neutral will be available. We can measure either only Phase to phase Voltage or only Phase to neutral voltage or both can be measured, right?  So, Neutral is not mandatory for this circuit as well as ADS131E04 , right?.

2. Hope -VE Supply for AVSS not required for ADS131M03/ADS131M04 ?

3. We are using CC3220MODSF12MOBR and PIC24FJ256GL406 in two different device.So, how can we supply Clock from MCU to ADS131M03/4 CLKIN pin? Kindly advice, can we use CLKO on PICPIC24FJ256GL406? And we unable to found CLKO on CC3220, so kindly advice how we can supply CLK.

4. As per the sample circuit, Hope, -ve Supply is not mandatory for ADS131E04 ? But why in application circuit used -ve Supply? any advantage using -ve Supply?

5. 6 or 8 -channel is available in ADS131M series? because ADS131E04 circuit looks dense/more pins/components.

6. We need to measure the line Voltage, but we don't want to connect line to our device directly. How we can measure the Line Voltage with some isolation? Can we use Potential Step down transformer(PT) external to the device and connect Secondary PT to ADS131M04 or ADS131E04 inputs? Kindly suggest better way. 

7. SPI will gives RMS Voltage and Current or only ADC pin peak Voltage? Can we calculate Power Factor and active/reactive/apparent Power accurately?

Thanks and regards,

Naveen K

Hi Naveen,

I'm supporting ADS131M0x and ADS131E0x ADCs in the same team as Angel. Let me jump in and answer your questions:

1. Your understanding is correct. You can check the figure 9-3 in ADS131M08 datasheet and the following reference design for a better understanding:

    Cost-Effective, 3-Phase CT Electricity Meter Reference Design Using Standalone ADC

2. ADS131M0x ADCs do not have a AVSS pin, these ADCs can support bipolar analog input with a unipolar power supply because of internal negative charge pump. AVSS on ADS131E0x ADCs offers a bipolar power supply option to support true bipolar analog input if this is expected by you. ADS131E0x can also support unipolar power supply by providing an unipolar power supply to AVDD and shorting AVSS to DGND together.

3. Your can use external oscillator or a clock from your microcontroller, the reference design in the link above shows an example circuit for using CLKOUT of TI's MSPM0G1107 microcontroller as the master clock for ADS131M08 ADC, see the circuit on the first page of the reference design.

4. You do not have to use bipolar power supply on ADS131E0x as I explained above. Actually I would recommend you to use ADS131M0x ADC in your application.

5. Yes, see the datasheet of ADS131M08 and ADS131M06.

6. You can use high value resistor divider for phase voltage measurement, and also use CT(current transformer) for phase and neutral current measurement if needed. See the figure 9-3 in ADS131M08 datasheet and also the details in the reference design.

7. The ADC only outputs conversion code according to the voltage applied on the analog input. If you use TI's any Cortex microcontroller ( e.g. MSPM0G series), TI can provide Metrology Energy library which can be used to calculate the following parameters:   

    Active and Reactive Energy and Power, Root Mean Square(RMS) Current (live and neutral) and Voltage, Power Factor, Line Frequency Calculations, Line-  Line voltage, V/I Phase angle etc.

BR,

Dale

Hi Dale,

Thank you for the information.

1.  ADS131M0x or ADS131E0x ADCs is dedicated to CT/RMS voltage measurements or we can also connect DC Voltage based sensors or 4-20 mA Sensors like Temperature Sensors in Single ended type?

2. Internally, decided to use Energy Meter IC's to measure all the possible Harmonics like same as Energy meters. So kindly suggest the Energy Meter IC for 3-phase rms Voltage, Current, Power,Energy, Frequency and Harmonics, etc...

3. Additionally, For Any dc voltage/current based analog Sensors interface like 4-20mA Temperature Sensors or 0-xVdc analog voltage measurement with 4-Channel, Energy meter IC having additional Analog Inputs or we need to use another ADC IC? If Energy meter IC doesn't have additional ADC pins and we need to use another ADC IC, then we need to use ADS131M0x or ADS131E0x or any other cost-effective ADC ic will be available?

Thanks and regards,

Naveen K

Hi Naveen,

We had a holiday yesterday. I will look into the details and get it back to you soon.

Regards,

Dale

Hi Naveen,

Please see my answers below:

1. These ADCs can sample any analog signal as long as the input signal meets the requirement of the ADC (e.g. AGND-1.3V~AVDD absolute input voltage range when Gain is less than 8). ADS131M0x can directly accept bipolar input single-ended signal (lower than AGND, 0V) on AINxP pin while the negative input pin AINxN can be shorted to AGND. ADS131E0X can also accept single-ended input signal but the ADC input should be configured in pseudo-differential input for unipolar AVDD, or the single-ended input can be connect to AINxP and the negative input pin AINxN is directly shorted to AGND when AVDD/AVSS are bipolar power supplies, so there is no problem for these ADCs to sample a DC voltage or a signal from temperature sensor via 4-20mA current loop.

2. Both ADCs are popularly used for E- Metering application. We have many reference design based on these ADCs on TI.com, below is one of them.

    Cost-Effective, 3-Phase CT Electricity Meter Ref. Design Using Standalone ADC

      ADC Energy Metrology Library can be used for getting these parameters you mentioned, this library was developed based on TI ADS131M0x ADC and TI Arm® Cortex® MCU.

3. These ADCs have different versions for multiple input channels, e.g. ADS131M08 has 8 analog input channels, ADS131M06 has 6 input channels, we also have ADS131M04/M03/M02 ADCs, you can select any of them according to your design requirement. 

I strongly suggest your check the datasheet of these ADCs first.

BR,

Dale

Hi Dale,

Thank you for the information.

1. Yes, sure. Suggested ADC can be used in Energy Meter Applications.

2. Just to understand, External ADC(Like ADS131M04) will be more Accurate or MCU(CC3220MODSF/MSP430) Internal ADC will be more Accurate for DC/Analog Sensors?

3. Hope Texas Instruments doesn't have 3-Phase Energy Meter IC like Analog Devices ADE7758  and Microchip ATM90E36A, right?

Thanks and regards,

Naveen K

Hi Dale,

Thank you for the information and well appreciated your support.

I will start with new thread whenever your support required on ADS131M0X.

Thanks and regards,

Naveen K