PGA460: 2 zones application, less than 2 meters

Interesting thanks. The issue with bistatic open top is the (ugly) impact on the design because od transducer diameter.
I think that we can deal with a blind zone of 10/20 cm (not so blind because if an object is very close to the trasnducer, the "background" will disappear).
Would you have any suggestions for low profile open-top transducer ?
I am currently evaluating the PGA460 EVM with MA58MF14 transducer. I am trying to detect people at 2m/2.5m and that does not look obvious (signal very close to noise). Would you suggest a good EVM setting optimized for detecting people around 2m ? Is is possible to still detect people with MA58MF14 and OGA 460 inside a thin plastic casing ?
thanks for your help.

Hi Stan,
The Murata MA85MF14-7N should be able to detect a 75mm pole (automotive ISO-pole standard) up to at least 5m. I recommend you use the device settings loaded by the PGA460-Q1 EVM GUI's Device Settings --> General page --> Default All Register Settings box --> muRata MA58MF14-7N ISO-Pole button. This will populate all register settings to optimize ISO-pole detection up to 5m. If you are only using the USB-boost supply for 7.2V operation, you may be limited to 4m or 4.5m ISO-pole detection.

You'll notice the EVM also includes the muRata MA40H1S-R surface mount transducer on the direct-drive half of the EVM daughtercard. This is the only SMD ultrasonic transducer available on the market today. If you are seeking a low profile open-top transducer, this is the lowest available. Otherwise, the muRata MA40S4S/R barrel-type open-top pair is very reliable.

All transducers typically perform only when coupled directly to air. The moment you add any plastic or sheeting to cover the transducer's face, performance will decrease significantly. It may be possible to detect upward of a few meters, but only through very thin plastics or sheets of waterproof materials. Based on preliminary testing with the muRata MA58MF14-7N, I have successfully detected objects up to 2m through 0.093" of polycarbonate. However, other materials have proven to be less effective (i.e. acrylic) or not effective at all (i.e. glass and steel). Meanwhile, when using the SensComp 40LPT16, I can detect beyond 2m through a loose sheet of polyethylene plastic resin (Ziploc bag). We are still investigating this topic of through-transmission medium testing. You'll need to experiment on different materials and thicknesses yourself since performance varies for each type of transducer/frequency.

hello Akeem Whitehead

Finally am getting a perfect ultrasonic measurement result response from PGA460.

Now i am thinking about which burst i can use first. Which is first either p1bl or p2bl.

My application is level measurement in tanks and sumps. 

Am using p1bl for short range measurement i.e less than 30inches and greater than 7 inches.

And p2bl for long range measurement i.e greater than 30 inches.

And one more thing is using 2 closed top transducers combination. 

I cant get the values below 7 inches. Blind zone is 7 inches in my design. 

Please suggest me is there any chance to reduce blind zone.

Hi Pradeep,

Which specific transducer part number(s) are you using for your bi-static pair?
Are you using the transformer drive or half-bridge direct drive mode?
In a bi-static mode, you should be able to detect below 7in (17cm).

My first recommendation is that you tune your transducer using external passives according to the PGA460 Ultrasonic Module Hardware and Software Optimization AppNote (www.ti.com/.../slaa732). Transformer drivers will require a damping resistor and/or tuning cap, while a direct-driver will only require a damping resistor.

Secondary, ensure that you are not saturating your return data via the time varying gain (TVG) or digital gain multipliers (DGM).

Can you provide your register settings (export memory map from GUI), supply voltage value, and example of the echo data dump output for no-object and an object at 7in?

hello akeem whitehead,

We dont know the part no of ultrasonic transducer. But i can attach picture of 40 Khz transducer what am using.

40 Khz 16 mm ultrasonic probe.

Am using transformer(IFT) driven mode for my distance sensing application.  

Yes am using both tuning capacitor(680pf) and damping resistor(10k ohms).

Currently am not using TVG. Am suing constant gain ranges from 32 to 64 dB.

i just done separate register settings for long rage measurement(30 inch to 150 inch) and short range measurement(7 inch to 30 inch).

1.  for short range mesurement these are my eeprom register settings.

USER_DATA1 = 0x00; USER_DATA2 = 0x00;USER_DATA3 = 0x00;USER_DATA4 = 0x00;USER_DATA5 = 0x00;USER_DATA6 = 0x00;USER_DATA7 = 0x00;

USER_DATA8 = 0x00;USER_DATA9 = 0x00;USER_DATA10 = 0x00;USER_DATA11 = 0x00;USER_DATA12 = 0x00;USER_DATA13 = 0x00;USER_DATA14 = 0x00;USER_DATA15 = 0x00;

USER_DATA16 = 0x00;USER_DATA17 = 0x00;USER_DATA18 = 0x00;USER_DATA19 = 0x00;USER_DATA20 = 0x00;TVGAIN0 = 0x88;

TVGAIN1 = 0x00;TVGAIN2 = 0x00;TVGAIN3 = 0x00;TVGAIN4 = 0x00;TVGAIN5 = 0x00;TVGAIN6 = 0x00;

INIT_GAIN = 0x18;FREQUENCY = 0x40;DEADTIME = 0xA0;PULSE_P1 = 0x8F;

PULSE_P2 = 0x00;CURR_LIM_P1 = 0x35;CURR_LIM_P2 = 0x95;REC_LENGTH = 0x52;

FREQ_DIAG = 0x33;SAT_FDIAG_TH = 0xEF;FVOLT_DEC = 0x7C;DECPL_TEMP = 0xCF;

DSP_SCALE = 0x00;TEMP_TRIM = 0x00;P1_GAIN_CTRL = 0x12;P2_GAIN_CTRL = 0x09;

these are my threshold registers for short range

P1_THR_0 = 0x80;
P1_THR_1 = 0x88;
P1_THR_2 = 0x88;
P1_THR_3 = 0x88;
P1_THR_4 = 0x88;
P1_THR_5 = 0x88;
P1_THR_6 = 0xF9;
P1_THR_7 = 0xCE;
P1_THR_8 = 0x73;
P1_THR_9 = 0x9C;
P1_THR_10 = 0xE7;
P1_THR_11 = 0x3F;
P1_THR_12 = 0x3F;
P1_THR_13 = 0x3F;
P1_THR_14 = 0x3F;
P1_THR_15 = 0x07;

2.for long range mesurement these are my eeprom register settings.

USER_DATA1 = 0x00; USER_DATA2 = 0x00;USER_DATA3 = 0x00;USER_DATA4 = 0x00;USER_DATA5 = 0x00;USER_DATA6 = 0x00;USER_DATA7 = 0x00;

USER_DATA8 = 0x00;USER_DATA9 = 0x00;USER_DATA10 = 0x00;USER_DATA11 = 0x00;USER_DATA12 = 0x00;USER_DATA13 = 0x00;USER_DATA14 = 0x00;USER_DATA15 = 0x00;

USER_DATA16 = 0x00;USER_DATA17 = 0x00;USER_DATA18 = 0x00;USER_DATA19 = 0x00;USER_DATA20 = 0x00;TVGAIN0 = 0x88;

TVGAIN1 = 0x00;TVGAIN2 = 0x00;TVGAIN3 = 0x00;TVGAIN4 = 0x00;TVGAIN5 = 0x00;TVGAIN6 = 0x00;

INIT_GAIN = 0x94;FREQUENCY = 0x40;DEADTIME = 0xA0;PULSE_P1 = 0x28;

PULSE_P2 = 0x00;CURR_LIM_P1 = 0x35;CURR_LIM_P2 = 0x95;REC_LENGTH = 0x88;

FREQ_DIAG = 0x33;SAT_FDIAG_TH = 0xEF;FVOLT_DEC = 0x7C;DECPL_TEMP = 0xCF;

DSP_SCALE = 0x00;TEMP_TRIM = 0x00;P1_GAIN_CTRL = 0x12;P2_GAIN_CTRL = 0x09;

these are my threshold registers for short range

P1_THR_0 = 0xB0;
P1_THR_1 = 0x88;
P1_THR_2 = 0x88;
P1_THR_3 = 0x88;
P1_THR_4 = 0x88;
P1_THR_5 = 0x88;
P1_THR_6 = 0xF9;
P1_THR_7 = 0xCE;
P1_THR_8 = 0x73;
P1_THR_9 = 0x9C;
P1_THR_10 = 0xE7;
P1_THR_11 = 0x3F;
P1_THR_12 = 0x3F;
P1_THR_13 = 0x3F;
P1_THR_14 = 0x3F;
P1_THR_15 = 0x07;

Hello Akeem whitehead

Do u have any suggestion on my register configuration. 

Help me out with my configuration.

Advance thanks. 

Hi Pradeep,

Since you are not using the Murata MA58MF14-7N, the damping resistor and tuning capacitor values may not necessarily be optimized for the 40kHz transducer you are using. The 10kOhm and 680pF values are optimized specifically for the TDK EPCOS transformer and Murata transducer combination included with the EVM. Since the part number is unknown, it is difficult for me to provide any recommendation (also your picture did not attach), so you will need to sweep various combinations. In this case, a 40kHz vs 58kHz matching circuit will most likely require different values for short range optimization.

In addition to the register map configuration that you provided above, can you also provide an example data dump output of a Preset 1 and Preset 2 burst-and-listen command? I would like to compare your output to the Murata's performance. Note, a 40kHz transducer will typically have a longer decay time due to the lower frequency. Thus, you may only be able to reliably detect downwards of 15~20cm with a mono-static 40kHz transducer after optimization (based on my experience).