General Application

The EGM module Type 701 item 731778 is a module of the HSE PLUGSYS measuring system and is used for capturing and amplifying ECG signals according Einthoven and Goldberger. Four electrodes are connected up. This module incorporates isolating input amplifiers in order to avoid hum interference. In this way the inputs are isolated from the output circuits and from the housing. The isolation barrier can withstand voltages up to 200 Volts.

The 6 output voltages of the different leads (I, II,III, aVR, aVL, aVF) can be linked through jumpers to the PLUGSYS system bus. From there the signals can be taken for ECG recording via a 8 or 16 channel USB control module to our DSI Ponemah-Cardio data a cquisition. Other DAQ systems can also be connected via the BNC outputs. A square-wave calibration generator with a 1 mV amplitude is incorporated for easy calibrating the amplitudes.

In addition the CTP (Central Terminal Point) signal is available at the input connector. This signal is required for operating the Wilson Lead Amplifier (WLA) PLUGSYS module Type 702. It serves as reference for the unipolar chest leads (V1 - V6) according to Wilson. For use, the EGM module has to be installed in a PLUGSYS housing Series 600.

Installing the module in a housing

If you have ordered a complete system your module is likely already installed and you can skip ahead.

Brief procedure:

• Pull out the mains plug on the housing.
• Remove the blank panel(s) at the housing slot position intended for the EGM module.
• Prepare the module (set lines and links)
• Insert the EGM module, note the guide rails.
• Push the module firmly into the bus connector. 
• Screw on the front panel.
• Plug in the the input cable and connect up the electrodes
• Reconnect the mains plug to the housing.
• Switch on the housing.

Internal instrument settings, jumpers

Warning: The EGM module has to be protected against electrostatic discharges while it is outside the housing!
The EGM module contains highly sensitive components which can be damaged or destroyed by electrostatic discharges. If you are removing the module from the housing or carry out any operations on the module outside the housing you must ensure potential equilibration before touching part of the printed circuit. (Touch an earthed item, such as earthed housing, PLUGSYS housing or similar).

Before you install the EGM module into the PLUGSYS housing it is necessary to set 6 cable jumpers on the circuit board in order that the output signals are linked to the appropriate or required bus lines. The module can only be used as intended if the bus lines have been connected up correctly. Do not forget to enter the selected signal assignment in the bus diagram for the PLUGSYS housing (the bus diagram is filed in the Operating Manual folder of the PLUGSYS housing under Section 1). If the module is supplied as part of a completely installed PLUGSYS measuring system, the operations described below have already been completed and the selected signal paths have been entered in the bus diagram.

NOTE: When selecting the bus line (AV1...16) be sure to use a free line and check this in the bus diagram. If there is no appropriate information in the bus diagram you can determine the bus line assignment only by removing all the modules and determining the signal paths selected on them using the corresponding operating instructions.

The position of the cable jumpers is shown in Fig. 2. 6 analogue outputs (A1 to A6) have to be linked to the required bus lines (AV1 to AV16). If the "QUICK START" function is to be operated not only with the key on the front panel but also centrally via the system bus, it is necessary to set also the jumper X.

Cable jumpers A1 to A6: The signals of the various ECG leads are carried on the cable jumpers marked A1 to A6. The connectors of these cable jumpers have to be plugged on to the pins for the analogue bus lines (AV1 to  AV16). The individual cable jumpers carry the following ECG leads:
 

Jumper X: The "QUICK START" function can be activated generally by pressing the "QUICK START" key. When several amplifiers are being used simultaneously (e.g. module WLA for unipolar chest leads after Wilson) it may be desirable to operate this function centrally. In this case the jumpers X of all the modules have to be set to the same line of the trigger bus TRIG1 to TRIG4. If this trigger line is then activated, either manually by a central key or e.g. by a PC connected to this line, a quick start is performed simultaneously on all modules connected to this trigger line. As an example, Fig. 2 shows the jumper X1 set to trigger line TRIG1.

Note: when selecting the trigger line (TRIG1 - TRIG4), be sure to use a free line and check this in the trigger bus diagram (the trigger bus diagram is filed in the Operating Manual folder of the PLUGSYS housing under Section 1). If there is no appropriate information in the diagram you can determine the bus line assignment only by removing all the modules and determining the signal paths selected on them using the corresponding operating instructions.

Do not forget to enter the selected trigger signal assignment in the trigger bus diagram for the PLUGSYS housing (the trigger bus diagram is filed in the Operating Manual folder of the PLUGSYS housing under Section 1). If central triggering of quick start is not required, the jumper has to be placed in the parking position (jumper X in Fig. 2).

Starting Up

After the ECG input cable or the input box has been connected to the input socket, and the output sockets have been connected to a data acquisition monitoring system you can switch on the housing.

Note: It is essential that the outputs are correctly connected to the individual channels of the DAQ system (visualization unit) and mark the channels with the appropriate leads (I, II, III, aVR, aVL, aVF).

Check first the function of the entire measurement system from EGM to the visualization unit by switching off the input on the EGM, setting the gain to 1000 and switching on the calibration generator: 

• Set switch "INPUT" to "OFF"
• Set switch "GAIN x1000" to "1"
• Set switch "CAL. 1 mV" to "ON".

All 6 outputs then show a square-wave signal with a frequency of 2 Hz (= 120 min-1) and an amplitude of 1 Volt. This signal can be used for calibration the connected data acquisition system 

During recording the switches should be set to the following positions:

• Switch "CAL 1 mV" to "OFF"
• Switch "FILTER (Hz)" to "200"
• Switch "GAIN x1000" to "1"
• Switch "INPUT" to "ON"

"GAIN" and "FILTER" may require a different setting depending on the actual conditions of your experiment.

Signal Input

The input socket of the EGM module is an 8-way RJ-45 socket. The front view of the socket with marking of the contact numbers is shown in Fig. 3. The contacts are used as follows:

Input Cable

Two versions of the input cable are available as well as an input box which have to be ordered separately.

Input cable with 4 needle electrodes for use on small animals.

Input cable with 4 banana plugs for universal use. Crocodile clips suitable for the banana plugs are available, so that many different electrode arrangements can be connected.

When using the EGM module in conjunction with the WLA module Type 702 (Wilson Lead Amplifier) the use of a special input box Type 701/2 is recommended which in addition to the extremity inputs of the EGM (RA, LA, RF and LF) provides also the 6 chest lead inputs of the WLA (V1 - V6). The connection of the CTP (from EGM to WLA) as required for the unipolar chest leads of the WLA is provided internally in the box.

Description of the controls

The item numbers in the descriptions below refer to Fig. 4.

1. Green LED. This lights up while the amplifier is switched on.
2. The "QUICK START" key serves to return the ECG signals quickly to the isoelectric line. This key has to be pressed for rapid "zeroing". The key acts simultaneously on all the leads. 
3. Switch "CAL 1 mV". When set to "ON" a square-wave calibration signal with a frequency of 120 min-1 (2 Hz) and an amplitude of 1 mV is generated and superimposed on the input signal. With the input switched off (switch INPUT set to OFF) the output carries the pure calibration signal. The calibration signal appears simultaneously on all leads but not synchron. The amplitude 1 mV is referred to the input and serves for evaluating the amplitude of the ECG signal. The calibration signal appears with different amplitudes depending on the selected gain setting (switch GAIN); at GAIN = 1000. output = 1 V; at GAIN = 500, output = 0.5 V; at GAIN = 2000, output = 2 V.
4. Switch "FILTER (Hz)" "(HIGH CUT OFF)" is used to set the upper frequency limit. This filter permits some smoothing of the ECG signal. When selecting the filter setting, note that "excessive filtering" may reduce the amplitude of the steep parts of the trace (R-wave)! The switch setting should therefore always be selected from the top downwards, i.e. always start with 500 Hz, then switch to the lower steps (200 Hz - 100 Hz) and observe the amplitude (height of the R-wave). With excessive filtering the amplitude of the R-wave is reduced and the trace is no longer true. The filter acts simultaneously on all leads.
5. Switch "GAIN x1000". This switch selects the amplification for all leads simultaneously. The actual gain is obtained by multiplying the selected switch position by 1000: at "0.5" the gain is then x500, at "1" it is x1000, and at "2" it is x2000.
6. Switch "INPUT". Using this switch all signal inputs can be simultaneously switched on (position ON) and switched off (position OFF). The setting of the switch does not affect the input impedances of the input circuit.
7. Input socket (RJ45), 8-way (for details see Section 6.1). The input circuit of the isolating amplifier has a floating input and can withstand voltages up to 200 V DC.

Troubleshooting

Technical Data

Mechanical Data