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I am looking at the specifications of a device that produces a narrow pulse waveform, direct current, pulse duration < 1 ms, frequency variable from 5 to 500 Hz. The specs for this device say that the output currant is 1 mA. My question concerns the conventions of spec reporting:

Does output of such a waveform at 1 mA mean that the currant is one mA integrated over the period of the wave, including the slack time between pulses, or does it mean that that the currant is one mA during the pulses when the current is flowing? To put the question in simplest terms, suppose the frequency was i Hz. In a second, would the current flowing through the circuit be 1 mA, or 1 μA?

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  • \$\begingroup\$ it is usually specified by source impedance or max current at some peak voltage. This current is very low which any CMOS gate can generate. Current can be defined in many terms, peak, average or RMS but for simple logic pulse levels Imax output H & L or Ioh, Iol in all datasheets. If analog then Vo @ Imax are common terms. Normally the source impedance is much lower than the load for slow signals but lab generators are standardized to 50 Ohms for high frequency response reasons into 50 Ohm coax. Your signals are very low frequency and low current. Most hobby guys use a 555 IC timer for this. \$\endgroup\$
    – D.A.S.
    Commented Oct 16, 2016 at 23:40
  • \$\begingroup\$ Others might use a CMOS Schmitt Trigger inverter, an input cap, large feedback trim pot to make a square wave or use a dual TTL 74LS123 to make a 1/2ms one shot and the other half of dual 1-shot to vary the dwell from 0.5ms to 200ms with another large Pot and large cap using RC formula in the datasheet. so dual 1shot fixed pulse width can be done several ways. \$\endgroup\$
    – D.A.S.
    Commented Oct 16, 2016 at 23:44
  • \$\begingroup\$ buy this ebay.com/p/… multi-turn trimpot for f and pulse width ? or duty cycle ? > add DC supply. \$\endgroup\$
    – D.A.S.
    Commented Oct 17, 2016 at 0:14
  • \$\begingroup\$ @TonyStewart.EEsince'75 Thanks, Tony! Just to make sure I understand you correctly, your reply means that the rated current is the current during the pulse, correct? Sorry to be dense. \$\endgroup\$
    – andrewH
    Commented Oct 17, 2016 at 19:11
  • \$\begingroup\$ Yes I=V/R, so what V , what R or what are you needing "exactly" or what is it for? \$\endgroup\$
    – D.A.S.
    Commented Oct 17, 2016 at 20:44

1 Answer 1

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Traditional Chinese Medicine (TCM) generally use inductive spikes so the spikes are current sources and the needles provide low resistance of some value ( Not checked <10k Ohm?) So the voltage and current are very short in duration, which can be computed and the Power = Voltage * Current and times time = Energy which may be more of a factor. Then the muscles respond to stimulated pulses at a higher threshold which in turn stimulates the body's reaction to heal itself with a skilled practitioner.

So the specs would be for mA current max and possibly the inductance behind that current where a voltage can be generated much higher than the charge voltage according to the resistance in the path V=IR.

Generally I think 1 mA pulse into acupuncture needles might be 10K so V=1mA*10K = 10 V which would feel like a 9V battery on the tip of your tongue for a short pulse.

These can be measured in Joules ( or milli-joules [mJ] ) where 1 mJ = 1mW * 1 second or 1W for 1 millsecond or the current stored in the small inductor as E=1/2L*I^2 then released as a spike then they can vary the current or charge voltage and charge duration is fixed. But in your case I don't know. It may be the equivalent of 100V into 10K ohms for 1ms but electrode R rises from chemical reaction until turned, unless using patches.

The time constant of the discharge depends on contact resistance between two wires such that the internal inductor L and skin electrode pair, R becomes T=L/R = time, and the voltage, V = I * R or peak current * electrode pair Resistance , R.

For example a 9V battery across the tongue if a long duration compared to 1ms but comparable to the energy felt in acupuncture adjustments if the patient can handle it. More is better but, it is supposed to be comfortable not torture. But if you have migraines, then you know what torture is.

With more time, I could have a better Engineering spec, but this is off-the-cuff.

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