Heart Rate Noise Detector REV. 1.1
HR Noise Detector: quick reference rev. 1.1 Contents 1. INTRODUCTION... 1.1 2. TECHNICAL NOTES ON CARDIO RECEIVERS... 2.1 2.1. GENERAL INFORMATION... 2.1 2.2. ELECTROMAGNETIC INTERFERENCE FIELDS... 2.2 2.3. MECHANICAL VIBRATIONS... 2.2 2.4. POSITION OF THE RECEIVER... 2.3 3. HOW TO USE THE NOISE DETECTOR... 3.4 3.1. DEVICE MAIN PARTS... 3.4 3.2. FIRST START-UP... 3.4 3.3. FINDING ELECTROMAGNETIC NOISE... 3.4 3.4. NOISE DETECTOR SATURATION... 3.5 3.5. ADDITIONAL NOTES... 3.5 3.6. POSSIBLE SOLUTIONS IN THE PRESENCE OF ELECTROMAGNETIC FIELDS... 3.6 3.7. HR NOISE DETECTOR BATTERY REPLACEMENT... 3.6 3.8. EXAMPLE OF USAGE: CASE HISTORY... 3.7 Page i
HR Noise Detector: quick reference rev. 1.1 Page intentionally left blank. Page ii
HR Noise Detector: quick reference rev. 1.1 1. INTRODUCTION Electromagnetic interference are increasing due to the increase of electronic equipments in general, and the widest presence of our equipment on many facilities (hospitals, private customers ). This could affect, most of the time, correct heart rate reception on our machines and it could become really difficult to find out the real cause/source of the problem. That s why we developed the next device, that s very useful to find out electromagnetic noises and to understand the areas affected by it. We could finally prove the problem at customer, we could move machines on a free of noise area, or we could find the source of the noise, so that customer could find a way to switch it off or shield it, when possible. We could also use this device as a preventive instrument, to check in a site, before the installations, if any electromagnetic noises are present. This manual contains notices and symbols which have a specific meanings: Information about the operation in progress. Observation about the operation in progress. Page 1.1
HR Noise Detector: quick reference rev. 1.1 2. TECHNICAL NOTES ON CARDIO RECEIVERS 2.1. GENERAL INFORMATION Technogym utilizes Polar or Salutron technology for measuring the heart rate frequency of the person training on the machine. The system consists of: a transmitter (Chest Belt), worn by the person training on the machine, which uses 2 electrodes to detect the electrical activity of the heart, and transmits the measured heart rate, by sending an electromagnetic signal at a frequency of 5 KHz. A receiver, like the one in the figure below, installed in the machine, which consists of: an antenna a (coil), which receives the signal from the transmitter strap worn by the user. An integrated circuit b, which has the function of filtering the analog signal and generating a pulse train corresponding to the received heart rate. The receiver is connected to the CPU board by means of 3 wires used for: +5 Vdc power supply; Output signal (heart rate); Ground. The output is a digital signal that is normally at 5 Vdc and goes to 0 Vdc, for a few msec., when a heart beat is detected, as shown in the figure below. Find more detailed information about that on all Excite Service manuals. Page 2.1
HR Noise Detector: quick reference rev. 1.0 2.2. ELECTROMAGNETIC INTERFERENCE FIELDS There are 2 types of problems which can typically occur on the heart rate signals: 1) Electromagnetic interference: caused by disturbances from sources of electromagnetic noise. This problems could cause: higher heart rate signal: HR deviate from the real value, typically making it higher. Saturation: in this case the disturbances from sources of electromagnetic noise is so high that receiver is no longer able to detect any heart rate signal. Interference may occur near high voltage power lines, overhead lines of electrical railway, electric bus lines or trams, television, stereo speakers, neon lights, motors, computers, cell phones, air conditioning systems, electro-medical devices. Several pieces of equipment with electronic or electrical components, such as LED displays, motors, and electric brakes, may cause interference with stray signal. 2) Cross-talk: similar to the interference problem, but this is caused by reception of a signal from another Chest Belt, typically worn by users on adjacent machines, if they are too close together (less than 1mt radius, on average). This cause HR beats incorrect reading, with usually higher values, because the 2 signal received from the Chest Belts, can be summed together by the HR receiver. 2.3. MECHANICAL VIBRATIONS Mechanical vibrations may cause slight shifting of the coil, giving rise to transient impulses. If these transients occur only occasionally they can be easily filtered by SW. However, if the mechanical vibrations are periodic, they can produce periodic pulses which may be interpreted as correct heart rate values. To eliminate or reduce the effects of vibration the receiver is usually housed into a sponge (see pic. below). Page 2.2
HR Noise Detector: quick reference rev. 1.1 2.4. POSITION OF THE RECEIVER Carefully position the receiver according to the specifications below: the coil must be directed toward the user; the coil must be positioned well away (even a few centimeters) from the LEDs; the cable must be folded immediately after the connection on the receiver, so that it does not pass near the coil; the cable, from the receiver to the CPU board connector, should be properly routed in order to not pass over LEDs or electronic components that may cause interference. the receiver must be directed in such a way that its axis of reception is parallel to that of the transmitter, as shown in the figure below: Page 2.3
HR Noise Detector: quick reference rev. 1.0 3. HOW TO USE THE NOISE DETECTOR 3.1. DEVICE MAIN PARTS Indentification label Coil side/ position Red LED Switch on/off button If you tap your finger on the Noise Detector casing, when device is ON, Red LED will blink at each hit. This is because the noise generated by the vibration on the chassis, and can be used to check if unit is ON and battery works. Battery not included: refer to par.3.7 to install the battery the first time on the device. 3.2. FIRST START-UP First always check if Noise Detector is properly working attending the next steps: 1. Switch it ON and check if LED is blinking when tapping on the casing, as explained before. 2. Wear a wet Chest Belt transmitter and check if LED regularly flash on. Each LED blinking correspond to each heart rate beat detected. 3.3. FINDING ELECTROMAGNETIC NOISE The HR Noise Detector is really sensitive to all electromagnetic fields produced by the switching of LEDs, motor brushes, the commutation of power devices, monitors, neon lights, stereo equipment, etc Page 3.4
HR Noise Detector: quick reference rev. 1.1 This Noise Detector causes the LED to light for every heart beat and/or transient 5Khz frequency detected: in this way it is possible to determine whether there is electromagnetic noise, and identify its source. Keep the Noise Detector in your hand, with the coil to the front, and check around the TG machine and, in general, into the room to find possible electromagnetic noises. When you can see red LED repeatedly flashes, that means an electromagnetic noise has been found. Faster is the LED blinking frequency nearest is the electromagnetic noise source. The presence of electromagnetic noises is easily recognizable, respect standard Chest Belt HR beats, because generally accompanied by fast and irregular blinking of the LED. While Chest Belt beats are always regular in time (same blinking speed/same duty cycle). 3.4. NOISE DETECTOR SATURATION If an area is affected by high level of electromagnetic noise the Noise Detector may become completely saturated. This phenomenon, depending on its intensity, may cause the device impossible to receive any signal (LED always OFF), even if you wear a Chest Belt in front of it. In this case it s really important to have a well working and tested Chest Belt to test the Noise Detector, to avoid any doubts: if no signal is received by the Chest Belt as well, the Noise Detector is saturated. To prove it you can move into another room/ area to check when HR beats are detected again. 3.5. ADDITIONAL NOTES HR Noise Detector is very sensible. You can find at all the 5Khz spurious transient or periodic noise pulses. If you keep it nearby an ARM display, for example, LED will flash fast because display s LEDs and up create electromagnetic noise. That s why HR receiver, on our cardio machine, is always housed in a fixed and pre-tested position, far enough from ARM display or the other source of noise produced by our machines (mains power cables, AT/ALE driver, WTV/ Visio electronic boards ) You can use the Noise Detector to check if distance from machine to machine is enough to avoid cross talk phenomenon: when a user, wearing the Chest Belt, is training on one machine, you can check at which distance the Noise Detector can still display beats. This to prove at customer to respect the minimum machines required distance to avoid cross talking issues. Noise Detector, because its sensibility, can show beats even if you are far than 1mt from the user wearing the Chest Belt. Cardio receivers installed on machines instead have Page 3.5
HR Noise Detector: quick reference rev. 1.0 got an additional software filter that make them less sensible. So if machines minimum distance is respected, no cross talking issues will be present. From the other side we need such sensibility on Noise Detector, to face out all the possible issues (worst condition). Find more detailed information, about machines required minimum distance, on all Excite Service manuals. Usually HR on TG machines can work even if machines are a little bit too near between them, or even if a low level of electromagnetic noise is present around. Despite the Noise Detector sometimes flashes a little bit. This is because the additional software filter on cardio machines, just previously mentioned, and because when HR receiver succeed to link to the nearest Chest Belt transmitter, it properly works ignoring the noises around, when far and low. Vario Excite, by having the HR receiver far from the user, because the kind of frame and training, is more susceptible to electromagnetic noise and cross talking. In fact greater is the distance between HR receiver and Chest Belt, more difficult is for the receiver to succeed to link to the Chest Belt (because it can be engaged before by other HR signal or noises). That s why in presence of low noises, when other machines could still succeed to work, Vario could not. In this case it s enough to increase the distance of Vario from the noise source or from the other machines. 3.6. POSSIBLE SOLUTIONS IN THE PRESENCE OF ELECTROMAGNETIC FIELDS The only effective solution in the presence of electromagnetic interference is to reduce the power of the noise source, in 2 possible ways: Shielding the noise source. Increasing the distance between the noise source and the HR receiver, by changing the position of the machines or moving the noise source far from them, if possible. 3.7. HR NOISE DETECTOR BATTERY REPLACEMENT Open the back casing and replace the battery by a standard 9Volt ones. Page 3.6
HR Noise Detector: quick reference rev. 1.1 3.8. EXAMPLE OF USAGE: CASE HISTORY At a private house: Problem: Synchro Excite has got wrong heart rate beats during the training, usually after 10, 15 minutes of training. Wrong because higher than normal (suddenly HR freq. peaks). In the same room (basement room), there is also Recline and Run Excite that doesn t give any problem at all. Analysis: machine tested and HR works fine so it must be a noise that comes up after a while. Check performed by Noise Detector all around: a source of noise nearby the ceiling has been found. It s the floor heating plant of the upper room. Other machines are not affected because HR receiver and user are in a lower position than Synchro, and noise come from the high. Solution: ceiling has been properly shielded by a professional company committed by the customer. At a hospital: In a club: Problem: Vario Excite doesn t pick heart rate beats at all. All other Excite machines in the room are working fine (Run, Bike, Recline and Step). Analysis: check performed by Noise Detector nearby the Vario. No beats are showed at all, even by using a tested Chest Belt transmitter. Moving around in the room, nearby the other machines, Chest Belt beats are correctly showed. Analyzing all the area by using the Noise Detector we found that Vario was in a position, full of electromagnetic noise that made Noise Detector become saturated as well. Moreover Vario is much susceptible to noise than other machines (ref. par.3.5 Additional Note ). Solution: Vario has been moved in a free electromagnetic noise area. Problem: Bike Excite has got issues with HR frequency. Frequency is not always correct: sometimes disappears, sometimes is too high (220 beats), sometime doesn t change (keeps low). Analysis: check performed by Noise Detector. Bike is the last machine of a row, and it s placed at the room corner. Electromagnetic interference has been found nearby that corner. It came from a cabinet fixed to the floor containing some voltages regulators. Solution: Bike has been moved far enough from this noise. Page 3.7
HR Noise Detector: quick reference rev. 1.0 Page intentionally left blank Page 3.8
TECHNOGYM S.p.A. Via G. Perticari, 20 47035 Gambettola (FC) ITALIA Tel.: +39-0547-650638 Fax: +39-0547-650150 e-mail: service@technogym.com HR Noise Detector: quick reference rev. 1.0