How to use the HM250U Ultrasonic Height Stadiometer

Height is a commonly overlooked measurement that is more important than most people imagine, used for calculation of results such as Body Mass Index (BMI) and growth evaluation. This in turn can affect critical actions like medication dosage, which is something where there is little room for error!

 

What should you do if someone doesn't know their height? The obvious answer is of course to measure it, and not just guess. Typically, this is either done with wall-mounted or scale-mounted stadiometer, such as the Charder HM201M:

 

 

Or a free-standing portable height stadiometer, such as the Charder HM200P:

 

 

If you don't have an installed stadiometer, or if you're a traveling practitioner that doesn't have the time to set up a conventional portable stadiometer, then a portable stadiometer like the Charder HM250U is also a practical possibility!

 

Ultrasonic Height Stadiometers like the HM250U utilize a transmitter and receiver of ultrasonic waves, and the device measures the time it takes for the ultrasonic sound wave to fly from the sensor to the object and back again to calculate distance. A shorter time means the object is closer, and a longer time means the object is farther.

 

 

In the case of the HM250U, it measures the subject's height by measuring distance from the ground. Thus, it is important to make sure it is held upright when used, since if held at a tilt, the ultrasonic waves are received at an angle, and thus the results will indicate a longer distance.

 

The HM250U has a tilt detection system built into it, only allowing height measurement to complete if tilt is minimal (less than 5 degrees), thus ensuring results fall within acceptable accuracy range.

 

 

This means that if you don't hold the HM250U upright, the tilt lights will always be on, and it won't allow you to conduct a measurement! It can take a little bit of practice to learn how to hold the HM250U correctly and consistently, and here are a few tips to keep in mind:

 

Most people press the "measurement" button using their thumb. However, it's easy to accidentally shake the device when you press down on the button! To avoid doing this, we recommend holding the HM250U with one hand, and once it's steady, use your other hand to press the measurement button. 

 

(also, make sure the hand holding the HM250U isn't blocking the bottom sensor!)

 

If the HM250U is too close to the subject's body, the ultrasonic waves might bounce off their feet or body instead of the ground, affecting measurement accuracy. 

 

To avoid this, try and place the tip of the HM250U's head stopper on top of the subject's head (in other words, as far from their body as possible), and also make sure the operator's feet also are not in the way.

 

Due to the way ultrasonic waves work, the signal will be disrupted if it bounces off soft surfaces such as some carpets, or reflective surfaces like some marble/polished floors. 

 

 

For most accurate results, please make sure that the floor is hard and non-reflective.

 

Please feel free to contact Charder if you have any questions about using the HM250U correctly!