user65645: I'm using and ESP8266 with HC-SR04 ultrasonic sensor. The sensor requires 5v input and will also output to the GPIO pins at 5V. 
ESP8266 has a strong recommendation to use 3.3V into the GPIO pins. I've found some setups online with people using voltage dividers to bring the ECHO pin voltage down. 
Example on a PI: https://tutorials-raspberrypi.com/raspberry-pi-ultrasonic-sensor-hc-sr04/
I'm using a basic multimeter that i've found to be pretty accurate. When I put the BLACK cord on the ECHO and RED on the GROUND (of sensor pins), I get variable voltage readings. I'm trying to ensure a 3.3V coming from the ECHO into my ESP.
Questions: 

Am I putting the black and red cords on the appropriate areas? 
If yes to question 1, then why am i get such a variable of readings?
How can I test to ensure only 3.3V coming out of ECHO?


user4143: You have your leads backwards. But that doesn't matter, since there's nothing to measure. You'll only see a voltage (and even then only a brief pulse) when an echo is actually received.
You would need an oscilloscope to be able to read that voltage.

65645: <p>I'm using and ESP8266 with HC-SR04 ultrasonic sensor. The sensor requires 5v input and will also output to the GPIO pins at 5V. </p>

<p>ESP8266 has a strong recommendation to use 3.3V into the GPIO pins. I've found some setups online with people using voltage dividers to bring the ECHO pin voltage down. </p>

<p>Example on a PI: <a href="https://tutorials-raspberrypi.com/raspberry-pi-ultrasonic-sensor-hc-sr04/" rel="nofollow noreferrer">https://tutorials-raspberrypi.com/raspberry-pi-ultrasonic-sensor-hc-sr04/</a></p>

<p>I'm using a basic multimeter that i've found to be pretty accurate. When I put the BLACK cord on the ECHO and RED on the GROUND (of sensor pins), I get variable voltage readings. I'm trying to ensure a 3.3V coming from the ECHO into my ESP.
Questions: </p>

<ol>
<li>Am I putting the black and red cords on the appropriate areas? </li>
<li>If yes to question 1, then why am i get such a variable of readings?</li>
<li>How can I test to ensure only 3.3V coming out of ECHO?</li>
</ol>
 4143: <p>You have your leads backwards. But that doesn't matter, since there's nothing to measure. You'll only see a voltage (and even then only a brief pulse) when an echo is actually received.</p>

<p>You would need an oscilloscope to be able to read that voltage.</p>
