# Solving 90 Degree Phase Shift Problem with Acclerometer Signal

• morten84
OK, the answer is simple. Do you need lag/leading network? There are four typical topologies that are used to lag/lead a signal: T,Pi networks with passive components. T-network, Lag:Here is spice code for the networkR1 1 2 100C 2 0 1uR2 2 3 100 T-network, Lead:C1 1 2 1uR1 2 0 100C2 2 3 1uPi-network, LeadC1 1 0 1uR1

#### morten84

Hi.

I get a signal from an acclereometer that I integrate using an op-amp to get the velocity. But the problem is that this signal is phase shiftet 90 degree.
Because I'm supposed to compare this signal with a reference signal that is 180 degree phase shiftet, and now I'm getting wrong values.

Anyone know an easy way to phase shift this 90 degrees more, so that the total phase shift is 180?

OK, the answer is simple. Do you need lag/leading network? There are four typical topologies that are used to lag/lead a signal: T,Pi networks with passive components.

T-network, Lag:
Here is spice code for the network
Code:
R1  1  2  100
C   2  0   1u
R2  2 3   100

Code:
C1  1 2   1u
R1   2 0  100
C2  2  3  1u

Code:
C1  1  0   1u
R1  1   2   100
C2  2   0  1u

Pi-network, Lag
Code:
R1  1  0   100
C1  1   2   1u
R2  2   0  100

NB. values in the spice code are just arbitrary.

You just need to derive the transfer function for the network of interest, in
$$j\omega$$ terms and find the equation that defines phase shift (something with $$tan^{-1}()$$), so you'll basically need to work your way back. Just remember that those networks will also transform input/output impedance of your circuit and be sure to identify the frequency bandwidth of your accelerometer, so your phase lead/lag network won't interfere with the sensor.

BTW, that's the first time I've heard of need to shift the signal in order to get the accelerometer to function properly, I've worked with them before and have not experienced any problems with lagging. Probably because of the integrator.

P.S Are you Norwegian? Last edited:
morten84 said:
Hi.

I get a signal from an acclereometer that I integrate using an op-amp to get the velocity. But the problem is that this signal is phase shiftet 90 degree.
Because I'm supposed to compare this signal with a reference signal that is 180 degree phase shiftet, and now I'm getting wrong values.

Anyone know an easy way to phase shift this 90 degrees more, so that the total phase shift is 180?

Why would a reference signal be shifted by 180 degrees? If you have sinusoidal acceleration, you also have sinusoidal velocity variations, phase shifted by the 90 degrees. A 180 degree phase shift between a sinusoidal acceleration and the associated sinusoidal velocity plot would be non-physical.

you should be able to do it with an lcr circuit in the feedback loop of an op-amp.

## 1. How do accelerometers measure 90 degree phase shifts?

Accelerometers measure 90 degree phase shifts by detecting changes in acceleration, which is the rate of change of velocity. When an object experiences a 90 degree phase shift, it means that its velocity is changing at a constant rate, resulting in a constant acceleration.

## 2. Why is it important to solve 90 degree phase shift problems in accelerometer signals?

Solving 90 degree phase shift problems in accelerometer signals is important because it ensures accurate and reliable data. A 90 degree phase shift can introduce errors in the measurement of acceleration, which can impact the analysis and interpretation of the data.

## 3. What methods can be used to solve 90 degree phase shift problems in accelerometer signals?

There are several methods that can be used to solve 90 degree phase shift problems in accelerometer signals. These include signal filtering techniques, frequency domain analysis, and time-domain analysis. Each method has its advantages and limitations, and the choice of method depends on the specific application.

## 4. How can we prevent 90 degree phase shifts in accelerometer signals?

To prevent 90 degree phase shifts in accelerometer signals, it is important to properly calibrate the accelerometer and ensure that it is mounted correctly on the object being measured. Additionally, using high-quality accelerometers and avoiding external sources of interference can also help prevent 90 degree phase shifts.

## 5. Are there any common challenges in solving 90 degree phase shift problems in accelerometer signals?

Yes, there are some common challenges in solving 90 degree phase shift problems in accelerometer signals. These include noise and interference, non-linearity in the accelerometer's response, and the need for complex mathematical calculations. It is important to carefully consider these challenges and use appropriate techniques to overcome them when solving 90 degree phase shift problems.