General Application

The ECGA Item # 730149 module Type 689 is a module for the HSE PLUGSYS measurement system and serves for measurement system and serves for measuring and amplifying ECG signals. The input of this module incorporates an isolation between the input circuit and the output circuit and housing. The isolation barrier is capable of withstanding voltages up to 300 Volt. 

The ECG signal is indicated on a bar graph display. The frequency response of this module is arranged so that it can handle ECG signals up to 1000 bpm. The ECG signal is available as analogue voltage for recording at a BNC socket on the front panel and internally on the PLUGSYS system bus. A square-wave calibration generator with amplitudes of 0.3mV and 1 mV is incorporated to calibrate the ECG amplitudes. Before the ECGA module can be used it has to be installed in a PLUGSYS housing. As ECG recording and evaluation software we reccommend our DSI Ponemah-CARDIO software which has included an automatic ECG evaluation.   

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 ECGA module.
• Prepare the module (set lines and links)
• Insert the ECGA module, note the guide rails.
• Push the module firmly into the bus connector. 
• Screw on the front panel.
• Plug in the ECG cable
• Reconnect the mains plug to the housing.
• Switch on the housing.

Internal instrument settings:

WARNING: the ECGA module must be protected against electrostatic discharges while it is outside the housing! 

The ECGA module contains highly sensitive MOS components which can be damaged or destroyed by electrostatic discharges. If you dismantle the module or if you carry out any operations on the dismantled module you must ensure potential equilibration before touching any part of the printed circuit (by touching some grounded metal part, e.g. water tap, central heating radiator, grounded housing, PLUGSYS housing or similar). 

Before you install the ECGA module into the PLUGSYS housing it is necessary to set a link on the circuit board so that the output signal is linked to the appropriate or required bus line. The module can only be used in conjunction with the complete system if the bus line has 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 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. 

You can find the position of the links from the diagram below. The following link has to be set.

NOTE: If the amplifier is factory installed you do not have to set the link.

Signal Output for ECG to PLUGSYS bus system

In the example shown above the signal output has been set so the analogue ECG signal is on bus line AV 4.

Starting Up

After the ECG input cable has been connected to the input socket you can switch on the housing and start the measurement.

Calibration of a connected Data Acquisition System

The ECGA module incorporates a calibration generator for 0.3 mV and 1 mV pulses; this can be switched on by moving the switch "0.3/MEAS/1" to the appropriate position. In the description below it is assumed that the instrument is switched on, ready for use, and connected to a data acquisition system. 

As the ECG amplitude is usualy in the 1V range, best is to use the 1 mV calibration setting.

• Set switch "0.3/MES/1" to "MEAS"
• Set filter "High Cut Off" to 150Hz
• Set filter "Low Cut Off" to 0.1Hz
• Set "Gain" switch to "x1"
• Short-circuit the three input electrodes
• result will be a zero line at 0V. Read this value into your DAQ system as Zero mV
• Move switch "0.3/MEAS/1" to "1mV". The module now outputs a calibration signal with a 1mV amplitude (the calibration signal jumps from -0.5mV to +0.5mV). The shape of the signal depends on the filter setting. THe maximum of the signal corresponds to 0.5mV and the minimum to -0.5mV
• If you data acquisition has a max/min calibration feature you only have to assign the max to 0.5mV and the min to -0.5mV. Some systems read the maximum and the zero line. The maximum must be assigned to 0.5mV 

After completing this procedure you have arranged the required calibration. If now you move the switch "0.3/MEAS/1" to its center position "MEAS" you can record the ECG.

As a check you can switch back occasionally to "1" or "0.3" and check the deflections.

If you adjust the filter during the experiment you should check the calibration again and if necessary make a fine adjustment.

If the ECG signal goes beyond the selected range you can move the switch "x0.5/x1/x2" to position "x0.5" and thereby halve the amplitude. Warning, your DAQ system does not see this change as it only sees the voltage on the input. 

If the ECG signal appears too small you can move the switch "x0.5/x1/x2" to position "x2" and thereby double the amplitude.

NOTE: Every alteration in the amplification on the "GAIN" switch or the potentiometer also changes the calibration of the output amplitudes. 

The best way to avoid mistakes, after changing the amplification, consists of moving the switch "0.3/MEAS/1" to position "1" and to check the deflection which always corresponds to 1mV.

IMPORTANT:

In position 1 mV the square-wave signal is output with 1 mV jumps. Due to the automatic return of the signal to the zero line (AC coupling) the square-wave signal jumps from -0.5 mV to +0.5 mV (amplitude 1 mV). 

In position 0.3 mV a square-wave signal with 0.3 mV jumps is produced. Through the automatic return of the signal to the zero line (AC coupling) the square-wave signal then jumps from -0.15 mV to +0.15 mV (0.3 mV amplitude). 

The shape of the calibration signal alters with the filter setting "LOW FILTER CUT OFF". 
Below you see example with a chart recorder. Using a DAQ software should show the same waveforms. 



Input Pin Connections.

The ECGA module ahs a 5-pin Binder input socket with screw lock for an HSE ECG input cable. Only pins 1, 2 and 3 are used.

Description of the Controls

(1) Knob "FILTER HIGH CUT OFF" is used to set the upper frequency limit. This filter can be used to smooth the recording traces. It is important, however, to ensure always that filtering does not change the amplitude !

The adjustment is always made from the top downwards, i.e. always starting on 150 Hz, then switching down to 120 Hz and noting the amplitude (height of the R wave). The amplitude should not be reduced, otherwise filtering is already too strong. 

The heart rate alters with the animal species used. Rats, for example, have a heart rate up to 600 bpm and frequency components up to 120 Hz in the ECG signal. In this case the setting should always be 150 Hz or 120 Hz. With species having a lower heart rate it is possible to move to lower filter settings; however the amplitude of the R wave must always be checked.

(2) Knob "FILTER LOW CUT OFF" is used to set the lower frequency limit. This filter is used to set the time required by the signal to return to the isoelectric line (also known as AC coupling). A superimposed myogram, usually caused by thorax movement, can be filtered out through the setting of this filter.

(3) This is a fine adjustment of the amplification (GAIN) using a screwdriver. If the amplitude of the ECG signal is too large it can be reduced here. This fine adjustment is always linked to the switch "x0.5/x1/x2". During setting up it is preferable to use the "x1" position so that with an amplitude decrease or increase it remains possible to halve (x0.5) or double (x2) the signal without recalibration.

(4) Coarse amplification adjustment (GAIN) using the switch "x0.5/x1/x2". During setting up it is preferable to use the "x1" position so that with an amplitude decrease or increase it remains possible to halve (x0.5) or double (x2) the signal without recalibration.

(5) Switch "0.3/MEAS/1" to switch between calibration and measurement. The center position is the measurement position. In position "0.3" a calibration of 0.3 mV is simulated. AC coupling produces in this case a phasic signal with an amplitude of ±0.15 mV and the frequency of 3Hz (180 bpm) about the zero line.

In position "1" a signal with an amplitude ±0.5 mV appears at the output.

NOTE: after a change in the filter setting the calibration should be re-checked since a change in the filter may also influence the amplitude depending on the frequency of the ECG signal.

(6) BNC sockets ECG OUT (±10 V). This socket carries the ECG output signal in the voltage range ±10 V. This socket can be used for connection to an Oscilloscope or a Data Acquiistion system.

(7) Isolated 5-pin input socket. The input circuit of the isolation amplifier can withstand voltages up
to 300 Volt.

(8) Key "QUICK START" is used to return the ECG signal quickly to the isoelectric line. Press this key for rapid zeroing.

(9) LED "OUT OF RANGE". This LED lights up as soon as the voltage range of ±10 V is exceeded, The amplification (GAIN) is then too high and has to be reduced at the "GAIN" fine control or at the switch "x0.5/x1/x2".

(10) LED bar graph to visualize the ECG signal.
 

Troubleshooting

LED "OUT OF RANGE" flashing 

Amplification (GAIN) too high, R wave overloads ECG amplifier.

Technical Data