What is the power consumption of a weight sensor in a science fair project?

Click For Summary

Discussion Overview

The discussion revolves around the power consumption of weight sensors, particularly in the context of a science fair project. Participants explore when these sensors consume energy, the types of load cells used, and the specifics of their operation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks clarification on the power requirements of weight sensors and when they consume energy, questioning if it is only when weight is applied or continuously while active.
  • Another participant asks for details about the application and the type of load cells being used.
  • Some participants clarify the distinction between "censor" and "sensor," noting that certain weight sensors, like bathroom scales, do not require power to function.
  • It is mentioned that engineering load cells produce a voltage proportional to the load, while others argue that they produce resistance, which affects the applied voltage measured.
  • A participant describes a specific load cell configuration and provides calculations for power consumption, indicating that a 120 ohm bridge with 2V excitation would result in a current of 16.7mA and a power consumption of 33.3mW.
  • There is a discussion about different types of load cells, including piezoelectric cells that generate their own voltage output.

Areas of Agreement / Disagreement

Participants express differing views on the power consumption of weight sensors, the types of load cells, and their operational principles. No consensus is reached on these points.

Contextual Notes

Some statements depend on specific definitions of weight sensors and load cells, and there are unresolved details regarding the types of load cells and their configurations.

Tahmeed
Messages
81
Reaction score
4
I am making a science fair project, I need to know how much power a general weight censor needs, google doesn't seem to be helping.

And when a weight censor starts consuming energy?? when a certain weight is applied on it and it switches a circuit on, or as long as the weight censor remains active in the circuit??

Please help, I used google, but didn't get much benefit so looking for answers from you as my last option.
 
Engineering news on Phys.org
What is the application? What sort of thing is it weighing? How many load cells does it use?
 
Tahmeed said:
I am making a science fair project, I need to know how much power a general weight censor needs, google doesn't seem to be helping.

And when a weight censor starts consuming energy?? when a certain weight is applied on it and it switches a circuit on, or as long as the weight censor remains active in the circuit??

Please help, I used google, but didn't get much benefit so looking for answers from you as my last option.
There's a difference between a "censor" and a "sensor".

A weight sensor, like a bathroom scale, doesn't require any power to function.

Engineering load cells produce a voltage which is proportional to the load placed on the cell.
 
  • Like
Likes   Reactions: Madpoet626
SteamKing said:
There's a difference between a "censor" and a "sensor".

A weight sensor, like a bathroom scale, doesn't require any power to function.

Engineering load cells produce a voltage which is proportional to the load placed on the cell.

Sorry to be picky, but it would be more correct to say that engineering load cells produce a resistance that is proportional to the load that is placed on the cell. An applied voltage will then be varied according to that resistance and can then be measured.
 
Baluncore said:
What is the application? What sort of thing is it weighing? How many load cells does it use?

When a 500 gram or so load will be placed on a certain point, it will let the circuit start, when the load will be removed, the circuit will switch off.
 
Bandit127 said:
Sorry to be picky, but it would be more correct to say that engineering load cells produce a resistance that is proportional to the load that is placed on the cell. An applied voltage will then be varied according to that resistance and can then be measured.
What you say is true, for some cells, but other types produce their own voltage.

https://en.wikipedia.org/wiki/Load_cell

Specifically, the piezoelectric type is one such cell which produces its own voltage output.
 
  • Like
Likes   Reactions: Bandit127
A +/–1kg load cell will be made as a bridge configuration of 4 resistors. It will have 4 wires. A ratiometric ADC will normally read the differential output voltage and display it as weight.
But for your simple system you do not need the digital converter, only the sensor, an amplifier and a comparator will be required.

There will be a current flowing through the sensor while the sensor is receiving power. That will dominate the power consumption. A 120 ohm bridge with 2V excitation will need 2/120 = 16.7mA. The sensor power will therefore be 33.3mW.

http://www.hbm.com/en/menu/products/strain-gauges/stress-analysis/full-bridge-vy/
“The right resistance: The selection of the resistance depends on the constraints of the measurement task. Strain gauges of 120 ohms are relatively insensitive to fluctuations in the insulation resistance; for example, due to the effects of moisture.
The advantage of higher-impedance strain gauges is that they produce less specific heat due to the lower measuring current. In addition, they are less sensitive to resistances in the connecting cables to the measuring amplifier. There is also a disadvantage that high- impedance strain gauges may be more sensitive if noise pulses are received.”
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
Replies
11
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
7
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
Replies
6
Views
4K