settings for sampling at a rate vs fixed increment

I am currently working on a web app for a sensor. This sensor logs a value at set increments. In the settings, I want the user to be able to change the units of time they use. I also want them to be able to choose from logging at a rate, such as twice per second, or logging at a fixed interval, such as logging every two seconds. Currently, I have a drop down menu with the following items:

• / second
• / minute
• / hour
• seconds
• minutes
• hours

After they have selected one of these items, they enter the number in a box below. For example, if they chose the first option in the dropdown menu and the number 6, it would log 6 times per second. If they chose the 4th item in the dropdown menu and the number 6, it would log every 6 seconds.

After they have chosen a setting, text comes up confirming the setting they have chosen. However, I worry that this is not very user friendly and the user will not understand the difference between '/ second' and 'seconds' the first time they use the app. Can anyone suggest a more user-friendly way of giving the users the same options?