Heart Rate Monitor

Hi. I just wanted to run something by all of you. I have been using a polar HRM that I bought five years ago to keep track of my HR, Calories burned, etc. I think I had the battery replaced once by mailing it to a polar service center. Anyway, I've lost 13 lbs so far and working out a lot. When I used to run regularly I had a resting pulse in the low 60's. When I got out of shape it was more in the 70's or 80's. Recently I noticed my HRM said that my resting pulse was 45, and it seldom went over 100 even when my perceived level of exertion was high. I figured I better schedule an appointment with my doctor because maybe my High Blood Pressure medicine is too high, and it is making my pulse rate low and preventing me from giong to my MAX HR.

Yesterday I finally got to the gym to work out. On the rowing machine there were those low numbers again. Couldn't go much above 85. I thought, yup, time to go see the doctor. Then I switched to a precor cross trainer that had it's own HRM on it. A lot of machines pick up the signal from my HRM transmitter, and display it on the machine. The Machine said that my pulse rate was at 120, while my HRM was still in the 80's. My perceived exertion was more similar to the number on the machine than my HRM. I suddenly realized that the reason for my low numbers could be something mechanical on the HRM. I went into my closet and found another HRM that I hadn't opened yet (a Christmas gitt) and am wearing it now. My resting pulse is in the 60's again, and I haven't tried it out working out, but I bet it will show higher numbers on workout than I was getting with my old HRM.

My question to you is, How do you know if a reading from a hrm is accurate? Is it possible for a low battery to measure HR too low like this? How do you know the battery on the transmitter might be low? If my HRM was estimating my heart rate too low doesn't that mean the Calorie counts I've been posting for MFP would be too low?

Maybe I should go to the store and buy a brand new monitor. Don't need to go to my doctor due to HRM dysfunction.