jit_singh_tara
Full Member level 6
- Joined
- Dec 22, 2006
- Messages
- 325
- Helped
- 9
- Reputation
- 18
- Reaction score
- 4
- Trophy points
- 1,298
- Location
- Delhi , India
- Activity points
- 4,295
Dear friends ,
I have an application where i am connecting the load cell to a machine with ac motor.The machine shaft moves up and down through the contactors .
1. Machine is driven up or down from optocoupled outputs of the relays .The relays drive the contactors which move the machine up or down.
2.Load cell is connected to the machine mechanically bolted.
3.Load cell is powered from the pcb 5V and ground which are given to the load cell from the Uc card .
4.uC card contains other peripherals also whose ground is commonly connected to the Adc section , Load cell power supply and rest of the circuit except the relays and proximity sensors.
5. The motor is also connected to the machine(ac motor).
Now when the machine is not moving there is no peak on the load cell supply (it is almost smooth 5V dc) as seen on oscilloscope.
when the relay is turned on there is a very big visible spike around 10V on the Load cell supply .I know that as soon as motor is turned on there is a sudden spike which enters the circuit from the ground of the load cell which not only gives the false reading but disables the other sensitive devices like mcp2200 .
Please suggest me what to do in this situation .......How is load cell connected in such kind of an application .Is this kind of noise normal (i mean do we use some special technique to keep away the motor noise entering the circuit from load cell body .The noise pattern is consistent whenever the motor is switched on (contactor is switched on).
I am enclosing a screenshot of the image.
I want to keep my circuit free from this motor noise .And i also figured out that it exists only when the contactor is switched on ...... please suggest what could be done , as the circuit uses a high precision 16 bit adc , this noise is not at all acceptable.....
Thanks and regards....
Jitender singh
I have an application where i am connecting the load cell to a machine with ac motor.The machine shaft moves up and down through the contactors .
1. Machine is driven up or down from optocoupled outputs of the relays .The relays drive the contactors which move the machine up or down.
2.Load cell is connected to the machine mechanically bolted.
3.Load cell is powered from the pcb 5V and ground which are given to the load cell from the Uc card .
4.uC card contains other peripherals also whose ground is commonly connected to the Adc section , Load cell power supply and rest of the circuit except the relays and proximity sensors.
5. The motor is also connected to the machine(ac motor).
Now when the machine is not moving there is no peak on the load cell supply (it is almost smooth 5V dc) as seen on oscilloscope.
when the relay is turned on there is a very big visible spike around 10V on the Load cell supply .I know that as soon as motor is turned on there is a sudden spike which enters the circuit from the ground of the load cell which not only gives the false reading but disables the other sensitive devices like mcp2200 .
Please suggest me what to do in this situation .......How is load cell connected in such kind of an application .Is this kind of noise normal (i mean do we use some special technique to keep away the motor noise entering the circuit from load cell body .The noise pattern is consistent whenever the motor is switched on (contactor is switched on).
I am enclosing a screenshot of the image.
I want to keep my circuit free from this motor noise .And i also figured out that it exists only when the contactor is switched on ...... please suggest what could be done , as the circuit uses a high precision 16 bit adc , this noise is not at all acceptable.....
Thanks and regards....
Jitender singh