heart rate monitor on machine 10/30/05

My new favorite cardio machine wants heart rate constantly in order to keep me within fat burn range. With my weight and age (39!), it is 118 and it is fairly easy to reach. I noticed recently that depending on the machine, maybe this measurement of heart rate is not quite accurate. Yesterday I was on the machine, third from the left and I reached my target heart rate probably within under a minute. Then it kept asking me to slow down because heart rate is going too high. I never got to burn 300 calories being on the machine for 30 minutes! Today I used the one next to it and I never had to worry about my heart rate going too high. So it was comfortable and it says I burnt a little more than 300 calories. In the Experience magazine, I think those heart rate monitor is good for "fitness enthusiast". It will motivate you, but not exactly too accurate sometimes. I think I will avoid the third machine next time.