How to setup ultrasonic sensor to return values after 1 second

I am a new python and raspberry Pi user, I have run this regular code for ultrasonic sensor, the problem with it is that I have connected it to a system where it has continuous 5v input so it has no stop time --> resulting impossibility of stable distance measurement, I understood that I have to set a delay with time.sleep(1) somewhere to make it run for only 1 second for each measurement so it will get stable. My question is: where do I have to insert the delay? Is that answer right?

Code:

import RPi.GPIO as GPIO
import time

#GPIO Mode (BOARD / BCM)
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)

#set GPIO Pins
GPIO_TRIGGER = 21
GPIO_ECHO = 20

#set GPIO direction (IN / OUT)
GPIO.setup(GPIO_TRIGGER, GPIO.OUT)
GPIO.setup(GPIO_ECHO, GPIO.IN)

def distance():
    # set Trigger to HIGH
    GPIO.output(GPIO_TRIGGER, True)

    # set Trigger after 0.01ms to LOW
    time.sleep(0.001)
    GPIO.output(GPIO_TRIGGER, False)

    StartTime = time.time()
    StopTime = time.time()

    # save StartTime
    while GPIO.input(GPIO_ECHO) == 0:
        StartTime = time.time()

    # save time of arrival
    while GPIO.input(GPIO_ECHO) == 1:
        StopTime = time.time()

    # time difference between start and arrival
    TimeElapsed = StopTime - StartTime
    # multiply with the sonic speed (34300 cm/s)
    # and divide by 2, because there and back
    distance = (TimeElapsed * 34300) / 2

    return distance


if __name__ == '__main__':
    try:
        while True:
            dist = distance()
            print ("Measured Distance = %.1f cm" % dist)
            time.sleep(1)

        # Reset by pressing CTRL + C
    except KeyboardInterrupt:
        print("Measurement stopped by User")
        GPIO.cleanup()

Solution

First sensor only needs :

# set Trigger after 0.01ms to LOW
time.sleep(0.001)
GPIO.output(GPIO_TRIGGER, False)

that delay and you can put a your delay in main loop(yes you can add any number of seconds here). Second, Please add resistors for stable results because Ultrasonic sensor I/o's value is 0-5 volts but Raspberry pi GPIO deals in 3.3 volt check diagram from here: https://tutorials-raspberrypi.com/raspberry-pi-ultrasonic-sensor-hc-sr04/