Part Number: MSP430FR6043
您好，我将一段管道放入静止的清水中，使用ADC Capture可以捕获到完整波形，在Waveforms中的绝对飞行时间是58.12us。换能器之间的距离是72mm。温度的话室温是20摄氏度，水是放在室内的，具体多少度不知道，因为也看不懂里面的数据，请问里面的数据怎么阅读？
由此可以得到计算过程：v = s / t = 0.072 / 0.00005812 = 1238 m/s，而超声波在水中的速度是1450 m/s，我感觉差距有点大，请问怎么处理？
1. 所以针对我测出来的速度不太符合1450m/s的情况，我应该调小门限值
，但是我的门限值也挺小的了，应该能测到第一个波形了。如图本次测得的最大值是847，取11%是847 x 11% = 93.17，最接近第一个波（88）。此时的绝对飞行时间是57.21us，使用的是清水，速度就是换能器之间的距离除以绝对飞行时间，v = s / t = 0.062 / 0.00005721 = 1084 m/s，依然不符合1450m/s的理论值，环境温度是20摄氏度。
2. 您说得很对，我没有使能USS_ALG_ENABLE_ESTIMATE_TEMPERATURE ，使能之后读到的温度是215摄氏度，USS_TEMPERATURE_LUT_TRANSDUCER_CONST是使用的默认值0.04716，请问我需要根据什么修改它呢？
是的，我看错了，实际上换能器时间的距离是62mm。我将USS_ALG_ADC_ADDITIONAL_CAP_DLY 的值改成0了，将USS_TEMPERATURE_LUT_TRANSDUCER_CONST 改成了距离的一半，得到的温度是-72，请问这个是不是也不对，应该怎么让他读到正确的值呢？
The absTOF results are 57.10us when the temperature is -72 as shown in picture2. I don't know if the data of 57.10us is correct because envelope crossing threshold is 11%
. In theory, the first lobe is taken. Since clean water is used, the propagation speed calculated based on 57.10 is 0.062 / 0.00005710 = 1085 m/s, not 1450m/s.
I added a breakpoint at line 80, and the result is shown in picture3, I don't know if this is correct, I don't know what criteria to check it.
picture 1
picture2
picture3
I read 62mm on the website: https://item.taobao.com/item.htm?spm=a1z10.3-c-s.w4002-22815803607.11.33fd3856ibr0f3&id=673508863286
and I measured the distance with a ruler to be 62mm.
The 62mm is the distance the reflectors. What is the distance between the transducer and reflector?
I'm sorry. I don't know. I looked for it and it's not in the specs. The document TIDM-02005DesignGuide states that the distance is small enough to be negligible.
I see, if it's 10mm, the calculated velocity is about 1450m/s. But how do I get the right temperature? Is it related to the USS_computeTemperature function? I see there is a function USS_calculateVelocity to measure the velocity in it. Is the temperature related to the velocity? I don't understand why velocity was used as the 4th parameter to look it up in the table.
From pic1, C can be calculated from formula 3: C = L/2 x (1/T12 + 1/T21) = 0.62 / 2 x (1 / (5.71 x 10^-5) + 1 / (5.71 x 10^-5)) = 10858 m/s. In picture 2, there is no corresponding value of 10858, so it shows that the measured value is -72. If this is the reason, how do I get it to measure normal temperature?
picture 1
picture 2
Please use the following formula for calculation.
At zero flow, v = 0. So, C = (2L0+L1)/T1 or C = (2L0+L1)/T2. To do an average method, C = 0.5*((2L0+L1)/T1+(2L0+L1)/T2).
The L0 is not negligible in an actually design.
when L0 = 10mm, C = 0.5*((2L0+L1)/T1+(2L0+L1)/T2) = 0.5 x ( (2x0.01+0.062)/(5.71 x 10^-5) + (2x0.01+0.062)/(5.71 x 10^-5) ) = 1436 m/s
Figure 1 shows that 1436m/s corresponds to a temperature of about 8 ℃, but why is the temperature in the structure displayed as -72?
Figure 1
Figure 2
Could you check if you call the USS_computeTemperature function after calling USS_runAlgorithmsFixedPoint?
我把断点放在了USS_computeTemperature后面，USS_TEMPERATURE_LUT_TRANSDUCER_CONST改成了0.41，此时温度显示的是-4，但是现在这里开着26摄氏度的空调。
