A staff nurse who pretended to be a doctor and molested a patient was sentenced to seven months' jail on Wednesday.

Muhammad Ruzaini Johari, 33, was working as a staff nurse at a clinic in Yishun when he unclasped the 28-year-old woman's bra and placed electrodes on her chest.

Ruzaini, who is now a trainee deck cadet in a shipping company, was on an afternoon shift and had stayed behind in the clinic on May 11 last year to finish up some administrative tasks after the doctor on duty had left.

The woman and her husband, 33, who cannot be named due to a gag order, then showed up at the clinic as she was feeling unwell.

Although the doctor had already left, Ruzaini asked the woman to enter the consultation room, while he sat in the doctor's chair. He briefly examined her before asking her to lie on her back.

He lifted her blouse and started pressing her exposed stomach area. He continued to press down until he reached the area above her groin. The woman felt embarrassed but did not protest as she believed Ruzaini to be a doctor, the court heard.

Ruzaini then brought an electrocardiogram (ECG) machine, used to measure activity in a person's heart, to conduct a test on the woman despite knowing there was no reason to do so.

He lifted the woman's blouse to expose her chest and unclasped her bra to place the ECG electrodes on her breasts, wrists and ankles.

The woman became very uncomfortable and confronted Ruzaini. She removed the electrodes from her body, dressed herself and left the room.

Once outside, she burst into tears and told her husband what had happened. Ruzaini pleaded with the couple not to call the police but the husband made a police report.

Ruzaini pleaded guilty to one count of molestation.

District Judge Luke Tan called Ruzaini's crime "abhorrent and offensive".

He will begin serving his sentence on Aug 1 and is currently out on bail of $10,000.

Ruzaini could have been jailed for up to two years and fined or caned for outraging a woman's modesty.