Welcome, Guest

Author Topic: Re: SCJ325P00XG0B02G female jack  (Read 2269 times)

awjoy_tud

  • Newbie
  • *
  • Posts: 3
  • Karma: +0/-0
Re: SCJ325P00XG0B02G female jack
« on: June 07, 2016, 12:25:18 PM »
Hi ,
I am working with olimex shield EKG/EMG board. For the first experiment I am not using electrodes as an input for the board. Instead of that I want to use analog signal generator as an input on the board. Therefore I need to know how much(max or min) analog voltage its can take as an input. So that I can set my signal generator as an input between this range. Because if I give the analog voltage that exceed the range may be it will damage my board. So please give me some idea.

LubOlimex

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1819
  • Karma: +46/-2
Re: SCJ325P00XG0B02G female jack
« Reply #1 on: June 08, 2016, 12:58:12 PM »
SHIELD-EKG-EMG converts the analog differential signal (the ECG/EMG bio potentials generated by muscles), attached to its CH1_IN+/CH1_IN- inputs, into a single stream of data as output. The output signal is analog and have to be discretized further with aim to give the option of digital processing. Typically, this is done via dedicated ADC embedded in the MCU of the base board (like: OLIMEXINO-328, OLIMEXINO-32U4, OLIMEXINO-STM32, etc). In the demo example we have provided, "ShieldEkgEmgDemo.ino", we have used 10-bit ADC with 256Hz sampling rate.

You need to calibrate the board with a generator of micro volts (thousands of a volt). You can’t get volts from the skin of a human being - the unit was not designed with such input in mind. It was designed with micro Volts in mind.

Since such a generator might be hard to find we have provided the calibration signal generator pins. This square wave calibration signal is available at CAL connector. If you are using the default example the frequency of the calibration signal would be between 10Hz and 14Hz and if the shield is powered by 3.3V the voltage of the signal would be 165uVp-p +/-10%; if the shield works at 5V the voltage of the calibration signal would be 250uVp-p +/-10%. This signal can be used for calibration purposes if you connect it to the audio jacks. We use it during manufacturing to calibrate the gain of the boards to similar levels.

About the maximum voltage - the maximum analog voltage would be: the input voltage / maximum amplification

SHIELD-EKG-EMG’s total gain is the product of the gains of each discretization stage: Instrumental Amplifier(G1=10), OAmp with regulated gain(G2=6..101) and 3rd order "Besselworth" filter(G3=3.56). Then, the Gtotal = G1*G2*G3 = 10*(6..101)*3.56. By default, we have set the G2 gain somewhere around 80. Then, Gtotal = 10*80*3.56=2848. The 3rd order
"Besselworth" filter's cutoff frequency is set to fc = 40Hz.

Vmaxanalog = 3.0V/2848 ~ 1 mV

Best regards,
Lub/OLIMEX
Technical support and documentation manager at Olimex

Fany222

  • Newbie
  • *
  • Posts: 1
  • Karma: +0/-0
Re: SCJ325P00XG0B02G female jack
« Reply #2 on: February 27, 2017, 12:41:45 PM »
Hi,

i want to ask you about olimexino calibration pin. If connect calibration signal to input ECG, signal is destroyed by AC bond. Olimexino has a 0.16Hz high pass and output from arduino are DC pulses. I want to use this calibration signal to define calibration peak like a professional ECG 1mV (165uV for olimex board) reference pulse. Because pulses are destroyed by AC bond i canť use it. It is possible to use them?