Former sergeant Stephen Kirkpatrick, 36, was sentenced at Guildford Crown Court on Friday (July 30).
Kirkpatrick was charged following an allegation that he had an inappropriate relationship with a victim of domestic abuse in a case he was investigating.
Surrey Police referred the matter to the Independent Office for Police Conduct in January 2020 after the allegation came to light.
Kirkpatrick was based at Guildford Police Station but resigned from the Force in September 2020.
He pled guilty to the charge of misconduct in a public office at a previous court hearing.
Following his sentencing, internal misconduct proceedings against Kirkpatrick will now take place. Kirkpatrick was also ordered to carry out 200 hours of community work.
T/Assistant Chief Constable Alison Barlow said: “Police officers and staff work extremely hard to help and support the most vulnerable people in our communities day in and day out.
“In this case, former sergeant Kirkpatrick not only let a vulnerable victim down but also the wider public who place their trust in policing as well as his police colleagues.
“We expect professionalism from all our employees and this type of behaviour has no place in policing.
“Whilst he resigned from the Force almost a year ago, he will still face gross misconduct proceedings at a later date following his sentence in court.”