# Readout Theta Value and Phase Relationship
**URL:** https://forum.liquidinstruments.com/t/readout-theta-value-and-phase-relationship/1146
**Category:** Projects & Applications
**Created:** [March 17, 2025, 7:26pm UTC](https://forum.liquidinstruments.com/t/readout-theta-value-and-phase-relationship/1146 "2025-03-17T19:26:00Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@xiangyuwei](https://forum.liquidinstruments.com/u/xiangyuwei)
#### Post date: [March 17, 2025, 7:26pm UTC](https://forum.liquidinstruments.com/t/readout-theta-value-and-phase-relationship/1146/1 "2025-03-17T19:26:00Z")
Hi,
I would appreciate your clarification regarding the relationship between the readout theta value (in volts) and the phase (in degrees or radians) of lockin amplifier. Specifically:
- What is the exact formula to convert the theta voltage reading into phase?
- Does this conversion depend on the range of the R-T (Resistance-to-Theta) converter? If so, how?
Thank you,
Xiangyu
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### Author:  [@Dylan](https://forum.liquidinstruments.com/u/Dylan)
#### Post date: [March 26, 2025, 12:20am UTC](https://forum.liquidinstruments.com/t/readout-theta-value-and-phase-relationship/1146/2 "2025-03-26T00:20:14Z")
Hello,
If you define the phase shift as the phase of the input signal with respect to the local oscillator, then the equation is (360 degrees/ 1V) (V\_theta)= phi. For example, a phase shift of 90 degrees will result in a 250mV output.
If the incorrect voltage range is selected, this will affect your measurement. The voltage range you select should be based on your I and Q voltage levels
which are where the probe points are. You will want to select the smallest range possible, but not a range that is below your signal. This will result in a clipping of your signal and skew results. If you have any more questions please let me know!