Medical bed scale

Weight is an important medical physiological indicator that plays a crucial role in guiding doctors' diagnosis, particularly for critically ill patients. Monitoring weight is beneficial in preventing fluid overload or dehydration in these patients, enabling doctors to promptly diagnose and treat them. Currently, hospitals utilize beds with weighing functions to implement weight monitoring for critically ill patients who require long-term bed rest. 

1.Medical bed weighing composition Medical bed, load cell, junction box, A/D converter, microcontroller, display screen. 

2. Load sensor selection：

The selection of the structure and form of the weighing sensor in an electronic scale depends primarily on the structure of the scale and the environment in which it is used. Resistance strain gauge weighing sensors can be divided into compression-type weighing sensors and tension-type weighing sensors. For bed weighing, compression-type weighing sensors are generally chosen, with common structures including parallel beams, bellows, and shear beams. 

3. Consideration of the range of the weighing sensor: 

When using a weighing sensor, the weight of the scale body as well as factors such as vibration, impact, and offset load should be taken into account. Therefore, the principles for selecting the range of the weighing sensor may vary for different weighing systems. The general rule is as follows: 

For a known single-sensor static weighing system: (Fixed load + variable load) ≤ Rated load of the selected sensor * 70%.  

For example, if the weight of a patient is less than 270kg, the weight of the bed's weighing frame is 10kg, and the total weight to be measured by the sensor is 280kg, then the rated load of the sensor should be at least 400kg. 

4. Number of load cells Medical beds generally use a combination of 4 load cells. 

5. Load cell output voltage range 

The sensitivities of parallel beam and shear beam load cells are generally 2.0 and 3.0mv/v. 

Take parallel beam weighing as an example. The maximum range of the sensor is 400kg. Theoretically, the maximum output voltage = excitation voltage * sensitivity. The excitation voltage is 10V and the sensitivity is 2.0mv/v. Then the output voltage at the maximum range of 400kg = 10*2 =20mv. 

When measuring 280kg weight, the corresponding output voltage is 280*20/400=14mv. When considering that the weight of the bed's load-bearing frame itself is 10kg, its corresponding output voltage is 0.5mv, so the output voltage of the entire system is 0.5mv~14mv. 

6. Load cell installation 

Four sensors are generally installed on the bracket at the bottom of the hospital bed. The sensors are installed with one end fixed and one end stressed (see the figure below). 

7.A/D converter, microcontroller, display screen Our company does not provide this part for the time being, customers can purchase it separately according to their own needs.