TDC1000-C2000EVM: TDC1000-C2000EVM

Bharat Aravamudhan said:

Prabhakar,

In case you are using a Jar which has liquid in it and you plan to read the level from the bottom we would recommend that you use a 1MHz transducer.

Please check the plot of START, STOP & COMPIN pins. First check if you get the number of START that you have inputting in the TDC1000 Tab.

Also please try and increase the PGAGain and the Echo Thld value.

Thanks for this input Mr. Bharat. We tried the setup with a Plastic jar, Glass container with the 1MHz transducer. we fixed it using Glue (CYA) and hot glue packing. Also tried to fix the sensor using double-sided tapes.

In either case, the readings are not consistent. Values vary over long range of the order of seconds. This reading shows similar behavior with or without water.

We varied 1. NUM_TX 2. NUM_RX 3.PGA_GAIN and 4. ECHO-QUAL-THLD and 5. No of data for average as 50. We get expected reading once or twice only. Then, we get noisy answers. Num_ECHO is selected as Multi.

We get more repeatable responses while using double sided tapes. We are attaching sample graphs we got during these experiements.

Please review and share your suggestion.

Prabhakar,

Please send me pics of the START/STOP, COMPIN signals.

Hi Bharat,

We repeated the experiment with the same setup and captured signals on CRO. The CRO images of reading with water and air are attached. We dont see any difference in the reading displayed in the TDC1000-C2000 PC application.

CRO image captured in "Air" scenario: (1-Start, 2 - Comp-in, 3- Stop)

CRO image captured in "Water" scenario:

Setup:

1. Plastic container of size 7cm dia , transducer fixed using quick glue  2. Plastic container of size 12cm dia , transducer fixed with quick glue with hot glue dampening.

When we try this experiment in the same setup, the readings are varying from time to time. Please suggest what are the points to verify/consider in getting consistent and correct readings.

Prabhakar,

Let me review the data you have provided thus far. I will respond by Monday latest.

Prabhakar,

I am still working on this issue, I will get back with you before Friday.

Prabhakar,

Is the reading in your above plots correct as expected? The plots looks good and correct.

What level of variations do you see from time to time ?

Please refer to the document below on how to setup the transducer in plastic containers.

http://www.ti.com/lit/an/snaa266a/snaa266a.pdf

Hi Bharat,

Thanks for your reply. here are our response:

1. The reading is as expected. We also felt the plots  are correct.

2. When we repeat the experiments, we dont get the same reading.For instance, we get X microseconds in air and y microseconds with certain material either solid/powder/liquid. When we repeat the same again after few hours/minutes , we dont get the same readings. Either we get the same X microsconds or random value that varies between x to y microseconds. We are unable to conclude the correct configuration/settings or dont know what's happening.

3. We used the CYA glue and hot glue to fix the sensor on Glass and Plastic bottles. Readings are NOT repeating and hence the concern.

The TOF readings are matching in "air" scenarios. For the other cases, variation is much from the expected reading.

Please guide us.

Hi Bharat,

Just to add with above thread, I want describe by problem with my TOF experiment done on glass JAR results 

Jar: Glass Jar with 6cm diameter

The TOF results for below content inside Jar. These TOF values are NOT consistent across experiments for each material.

1) Empty (Air) - 350 to 552us 
2) Water - 40 to 500us
3) Rice - 15 to 40us
4) Dal - 350 to 550
5) Salt - 39 to 100us

If you see above, the results of Water and Dal are some times coming closer to Empty (Air).

1) Please suggest how to get consistent TOF results for each materials of Jar content?.

2) We have affixed the STEMINC Piezo (1MHz) transducer with CYA glue and hot glue (Fevi Kwik brand) on Glass jar outside surface. Do we need to have any Waveguide to maximise the ultrasound signal into Glass jar?.

3) Is this CYA glue/ Hot glue sufficient enough to transfer ultrasound into Jar glass wall and also into Jar content?.

Dear Bharat,

Thanks for your suggestions. We tried your suggestion 1 & 3. Option 2 is not feasible as we don't want to expose the electronics to the food material - as it is against our core design constraint.

We have increased the number of average cycle and increased the gain/reduced the threshold value. These options are helpful but not fully. All our trials are with Glass container only. Our observations are:

When we tried these options or did the experiments as per the TDC1000 documents, we are getting the TOF readings as expected. We checked this for even 5 to 10 times. But, when we repeat the testing (same setup) after few minutes, we don't get the same TOF readings. This puzzles us.

1. With a particular setup, we measured the TOF in empty Jar (only air) and got the value , say around 400 us. But , under the same setup we try after few minutes, the TOF value varies from 3us to 600 us. It takes many trials and repetitions and we might get the same reading after a long time.

2. We fill the jar with certain food material and try the TOF readings. For a particular material, we are getting the TOF value around 30-40 us. If we try to read TOF after few minutes, we don't get the same reading. The TOF readings now vary from 40 us to 500 us.

3. When we empty the jar and try to read TOF in empty condition again, the TOF reading varies randomly from 40 to 500 us , under the same setup. It takes 10s of minutes to come to stable to 400 us.

In a nutshell, 

1. we are not getting repeating values for our repeated trials.

2. under same setup, the values change drastically over a large range with or without any material in the jar.

The EVM configuration that gives good readings at the first trial is attached as screenshot here. Please help.

Hi Bharat,

We request your further guidance in resolving the erratic variation of TOF value.  Though refreshing the GUI results in better reading, the variations are misleading us. We are listing our observations as below:

1. When we measure TOF with empty (Air) condition, we get correct TOF. On trying with some material inside the Jar, the TOF value is random. If we reset and take another reading, the TOF value displayed is that of empty Jar . We are not getting TOF value corresponding to that of material. We may get the revised TOF value sometimes only (very random).

2. When we take reading without Blanking, we get a standard reading of TOF at around 40us for Jars of different size.

3. We want to have better clarity on the blanking and Timing Register. When we try with different Timing Register value, the TOF value changes drastically from Nil to maximum , say 700+us. Please share if there are any further documentation that clarifies the blanking and Timing register operations.

4. Please share detailed documentation on the GUI operations and functionalities to help us understand the TDC1000 and its matching GUI operations.

Appreciate your guidance and comments.