The Parenting Sense of Competence scale measures parental competence on two dimensions: Satisfaction and Efficacy. It is a 16 item Likert-scale questionnaire (on a 6 point scale ranging from strongly agree  to strongly disagree ), with nine questions under Satisfaction and seven under Efficacy. Satisfaction section examines the parents’ anxiety, motivation and frustration, while the Efficacy section looks at the parents’ competence, capability levels, and problem-solving abilities in their parental role.
The scale can also be a 17-point scale, as seen here (although as a 16-point scale, the last question isn’t used).
Scoring the PSOC: The scoring for the 17-point scale is found here (When scoring the PSOC, it is important to remember that several of the questions are reverse coded).
Some citation references for this scale are (the last two have public links to the publications’ pdfs):
Johnston, C., & Mash, E. J. (1989). A measure of parenting satisfaction and efficacy. Journal of Clinical Child Psychology, 18(2), 167-175. (who cite Gilbaud-Wallston & Wanderson, 1978).
Ohan, J. L., Leung, D. W., & Johnston, C. (2000). The Parenting Sense of Competence Scale: Evidence of a stable factor structure and validity. Canadian Journal of Behavioural Science/Revue canadienne des Sciences du comportement, 32(4), 251-261.