An Electrocardiogram mainly consists of several electronic and electrical components such as lead electrodes, connecting wires, amplifiers and storage & transmission devices. Edan’s SE-12 Express 12 channel ECG is a particular model that is extensively used in various health care facilities of the world. A description of the components of the device assembly is given as follows:
The electrodes that are used in the SE-12 Express model are mainly classified into two main types, unipolar and bipolar. The bipolar leads are used to measure and record the differential voltage between a subject’s wrists and legs. The bipolar electrodes are placed on the patient’s left leg, right wrist and the left wrist, thereby forming a triangular conduction pattern of the electrical impulses emanating from the heart, which are then recorded. Unipolar electrode leads, on the other hand, enable recording of the voltage difference between a particular reference electrode and the surface of the patient’s body to which the leads are connected or attached. Unipolar electrodes are connected to the right & left arms and to the right & left hands; moreover, the leads are also placed on certain specified areas of the patient’s chest. The ECG monitor is then used to view the patterns of the patient’s heart activity & note any change in the heart activities.
The amplifiers used in the model convert the weak electrical signal emanating from the human body and amplifies its magnitude so as to obtain a verifiable signal, which can be regulated, conditioned & thus, can be read on the monitor. The differential amplifier used helps in amplifying the relative difference between the reference signal & the low level signals obtained. The buffer amplifier is the first component of the ECG to which the input signals are transferred. The signal is received and then stabilized. Amplification of the input signal on a multiplier range of 5 to 10 is then done. The electrical network then converts the analog signal to its digital counterpart. The differential pre-amplifier in the device then conditions the signal by filtering and again amplifying the signal by a factor of 10 to 100. (Ti.com, 2016)
The SE-12 electrocardiogram typically shows output on a liquid crystal display monitor and on paper strip recorders. Computers and cathode ray oscilloscopes can also be interfaced with the device to observe and store data on various mediums. The data that is observed is almost always in a digital format and thus, the machine has several built-in analog to digital & digital to analog converter sections. The display device that is used in the model itself has certain microprocessors and dedicated electronic parts which help in properly creating & displaying the cardiograph waveforms on the display monitor. (Madehow.com, 2016)
Disassembly & Reassembly
Every part of the model can be replaced with file replaceable units and similar service parts and must be done by qualified personnel. A proper workflow chart must be followed in order to properly & correctly disassemble and reassemble the ECG device.
Module Frame Disassembly
The module frame release knob is pressed and the frame itself is turned by ninety degrees in order to make the module frame face right. The two snaps on the top of the front cover are then released. The four snaps on the inner part of the E-module slot are then released; the topmost two snaps are first released and then the lower two snaps are released. Finally, the cover unit is detached.
Recorder unit detachment is done after detaching the module frame front cover. The screws holding the recorder are unscrewed, ensuring no damage is done to the flex board on the recorder’s right. The recorder is then removed from the module frame. During reassembling, the recorder unit must be wholly installed into the module frame.
The PDM docking mechanism is then detached after properly removing of the module frame again; the inner left two latches are first released and then the mechanism itself is turned by thirty degrees so as to detach it from the board connector. Reassembling is done by reversing the steps of disassembling.
The module frame cover unit is then removed after the removal of the PDM docking mechanism by releasing the two adjoining snaps of the inside of the frame cover of the module followed by the detachment of the cover. Reassembling is done in the reverse order
The E-module interface board is disassembled only after the removal of all the above parts. The back plate of the device is removed with a flat blade screwdriver. The hinge flex board is disconnected from its connections with the module frames and then the screws of the e-module interface board are removed followed by removal of the board from the main unit. Reassembling of this component is done obviously in the reverse manner. (Edan.com.cn, 2016)
Finally, the whole module frame is removed by detaching its whole back plate and the hinge flex board from their respective frame connectors. Screws are removed and the snap behind the flex cable is released. The flap is lifted and the assembly is removed from the wall of the module frame.
Main Unit Disassembly
The main fuses are first replaced by pulling them out of the fuse holder.
The interface board plate is then detached from the frame; the actual board is then pulled out of the main unit.
The right house frame housing is then removed by releasing its snaps and then the left frame housing is similarly removed.
The top cover is then removed by pressing on the module frame release know and turning the frame by 90 deg. The tap cover is then detached by releasing its corresponding snaps.
After disassembling all the above components, the main unit is separated in to the rear & front units.
After this, the uDOM is detached, followed by detachment of the DC/DC board by detaching the battery cables and disconnecting the DC/DC board from the CPU board connector. During reassembling, the CPU board is assembled first, then the battery cable is connected and then the DC/DC board is attached. (Edanusa.com, 2016)
Front Unit Disassembly
The front assembly is detached after removing the side house decorations and the top cover. The WLAN card is then removed from the CPU and then the front unit is removed. The U/I cable is also disconnected from the user interface board. The reassembling of the parts is done in the reverse order.
The LCD unit is disassembled after the removal of the front unit assembly followed by disconnection of the display cables and then the disconnection of the two backlight cables from the inverter board. Reassembling is done in the reverse order.
Te backlight inverter board is then detached after removal of the side housings, top covers, WLAN card, font unit assembly and LCD unit. The inverter cable is then removed from eth backlight board and then the board is unscrewed. The steps are to be reversed during the reassembling process. (Edanusa SE-12 Series Electrocardiograph User Manual, 2011)
Next up the user interface board is removed. The screws are detached and the various cables connected to it are removed one by one. The trim knob is simultaneously removed by removing it from the front and detaching the nut & washer. The encoder cable of the trim knob is then detached from the user interface board and then the encoder itself is removed from the front unit. Reassembling is done in the reverse manner.
Edan.com.cn. (2016). Edan Instruments, Inc..
Edanusa SE-12 Series Electrocardiograph User Manual. (2011). 1st ed. Edan Instruments, INC. 2011.
Edanusa.com. (2016). EDAN USA :: Expanding Edan Medical Equipment Distribution into the USA :: Edan Instruments, Inc. :: EKG/ECG Resting Machines, Fetal Monitors, Ultrasound Machines, Dopplers, Pulse Oximeters, Veterinary Equipment.