You have choices in selecting a heart rate monitor. One of those choices is whether to choose an analog or a digital transmitter belt and watch or receiver. But, what is the difference between a digital and an analog heart rate monitor? And which of the two is best for you? The answer lies in how and where the body’s heart beats are signaled, transmitted, to the wrist top or other device and then shown on your display. And that signal, whether digital or analog, can make all of the difference to you and your success.
First, both digital and analog heart rate monitor transmitter chest belts detect the same electrical activity from the heart muscle’s contraction using sensors touching your skin. They measure the EKG/ECG or the electrical activity of the heart muscle. The sensor in your transmitter belt can be viewed by you – just look at the back side of the belt which goes next to your skin. On the back side and there is a soft and black rubber-like material that is often oval in shape. There are always two sensors – one on each side of the strap or belt – that detect the electrical changes in the heart beat by sensing the electrical activity of the heart muscle.
Both digital and analog transmitter chest straps and watches are equally accurate. What is different is how they transmit the heart rate electrical data to your device. With analog heart rate monitors, an analog transmitter chest strap sends an analog signal to it’s analog watch or other receiver; or with digital heart rate monitors, a digital transmitter chest strap broadcasts a digital signal to it’s digital watch receiver. The watch or the device does all of the calculations once the signals are received by it.
Analog transmitter straps detect each heart beat signal on its sensors and transmits a short wireless continuous electrical wave (see picture above). This signal is typically at wireless and low 5 Kilohertz frequency. The computerized logic on the electronic chip in the analog watch or receiver detects this wireless signal and then processes it in the analog receiver or watch to compute the beats per minute number. Each heart beat then is recognized by the watch as an independent event from any nearby user or other source of analog transmission on the same radio frequency. As a result, if there is more than one signal say from another nearby users or from a machine, like a treadmill for example, that signal can interfere or result in “cross talk” from the watch receiving multiple signals.
Analog heart rate monitors have the following advantages:
- Compatible with most of the cardio machines at the gym,
- Analog transmitters and receivers in the watch are less expensive, and
- The signal from the transmitter belt is carried through water so swimmers and those doing water activities like swimming or water aerobics can use a heart rate monitor.
The disadvantage of analog transmitter chest straps and watches is that if you are within about three feet of another analog signal the two signals that are broadcast from two different sources can lead to cross talk, interference. In this case, the analog watch will accept both signals from the two sources and add them together and you will get an incorrect heart rate number. When you separate the distance from the two sources by more than about three feet, then the watch will only receive the transmission from one user.
Similarly, digital transmitter chest straps detect each individual heart beat signal on its sensors and translates that data to a sequence of pulses. It’s a bit like Morse code – the data is sent into bits (on and off signals). The transmitter belt detects this cardiac signal, processes it on a logic board inside the belts, and transmits it wirelessly to the digital watch or device via an encoded packet of signals, typically at wireless 2.4 Gz frequency at a very fast speed, about 0.25 transmissions per second. These digital packets or the string of numbers are sent with one short burst for each heart beat detected. The digital watch receives the information in the packet and displays the data as heart rate in beats-per-minute on the digital watch. Since each transmissions is so rapid and since the digital signal uses binary code which comes from 0s an 1s there is no chance for interference. With digital heart rate monitors, there is no “cross talk”.
Digital heart rate monitors have the following advantages and disadvantages:
- The technology is newer (well, and more expensive than analog)
- Digital signals don’t interfere or “cross talk” with other users or other signals.
- Digital signals can be sent for longer distances
- Digital signals can be used with Bluetooth and ANT+ receivers in mobile devices like iPhones and others tools.
- Digital heart rate monitors will not work for most swimmers because digital signals do not transmit under water, unfortunately.
What’s the best heart rate monitor for you – digital or analog? If you are doing group exercise like Zumba® or boot camps or indoor cycling – get digital. But, if you are working out alone or with a personal trainer at a health club get an analog heart rate monitor because most cardio machines are equipped with analog receivers. If price is an issue analog heart rate monitors are much less expensive. If you can’t stand the interference from other analog heart rate monitors, then digital is better for you because there is no cross talk, and if you are a triathlete or a swimmer – well – the facts are that you will need both heart rate monitors – analog for swimming and digital for biking and running.
What to do? My answer – just get a digital and get a less expensive analog and you have the best of both worlds.
* Note: Some digital heart rate monitors use a new technology called ANT+, a wireless transmission protocol somewhat similar to Bluetooth. ANT+ is interoperable which means that different devices like power meters, heart rate monitors, speed-and-distance monitors can all talk to each other – regardless of the brand because they all speak the language, so to speak, called ANT+. Products that use ANT+ technology have additional wireless collision detection and changing transmission logic which further decreases the impact of cross talk. We recommend that you look for the ANT+ logo on your heart rate monitor if you are going to use more than one device because they all work together in unison.
*NOTE #2: The new bluetooth light heart rate transmitter belts are now available which transmit using the low power bluetooth protocol. I’ll be discussing this transmission protocol in the near future – but for now, they are rare, a bit proprietary, and sometimes hardware dependent.