Question

If a particular interval on the ECG graph paper is 1.5 small boxes in width, the interval would be measured as:

a) 2 millimeters
b) 0.06 seconds
c) 45 milliseconds
d) 600 milliseconds

Answer 1

The correct measurement for a 1.5 small box interval on ECG paper is 0.06 seconds. Calculating the maximum capacitance for an ECG circuit with a given resistance involves using the RC time constant formula. Limiting the capacitance to 100 pF or less in practice is typically achievable with careful circuit design.

Step-by-step explanation:

The student's question pertains to the measurement of time intervals on an ECG (electrocardiogram) tracing, where 1.5 small boxes on ECG paper correspond to a certain amount of time. ECG graph paper is standardized, with each small box representing 0.04 seconds. Therefore, 1.5 small boxes would represent 0.06 seconds in duration. This relates to the broader topic of ensuring that an ECG monitor has an adequate RC time constant to measure voltage variations over small time intervals effectively.

To calculate the maximum capacitance given a resistance of 1.00 kΩ and a desired RC time constant less than 100 us, we can use the formula τ = RC, where τ (tau) is the time constant. Solving for C gives us C = τ / R. Substituting the values, we get C = 100 x 10^-6 s / 1000 Ω = 100 x 10^-9 F, or 100 pF (picofarads).

As for practical considerations, in general, it is not difficult to limit the capacitance to 100 pF or less in an ECG circuit. ECG machines are designed with these specifications in mind, but care must be taken to ensure that the components used, and overall circuit design, do not introduce excessive capacitance.