It generates signal internally with the help of voltage control oscillator
It is a type of Pulse modulation as in PPM the position of pulse of carrier pulse train is varied in accordance with the modulating signal.
To calculate the parts per million (ppm) value in NMR spectroscopy, you use the formula: ppm = (δ - δ_ref) × 10^6, where δ is the chemical shift in hertz (Hz) of the resonance signal and δ_ref is the frequency of the reference signal (usually TMS at 0 ppm). First, determine the frequency of the NMR instrument (in MHz), convert the chemical shift from Hz to ppm by dividing by the instrument frequency, and then express it in ppm. This allows for a standardized comparison of chemical shifts across different magnetic field strengths.
Pulse-position modulation (PPM) encoding type always has a nonzero average amplitude. In PPM, the signal's average amplitude is determined by the positioning of the pulses within the signal. This ensures that there is always a nonzero amplitude level in the signal, even during silent periods.
PPM=Pulse Position Modulation is suited for data communications via optical fiber or short distance line-of-sight as in radio control models. A pulse is encoded by placing it in a specific position in time. Proper sync is required and transmission distortion can render it useless. FM=Frequency Modulation which is more suited for audio communications as in broadcast radio or personal communicators. The modulation of a carrier is accomplished by causing the frequency of the carrier to vary as a function of the audio. The speed of the variation is the frequency of the audio and the amount of the variation is the amplitude of the audio.
Pulse position modulation can be analog or digital, it depends on the signal and/or the modulator used to obtain the modulation. If an analog signal is applied at the input of the modulator, the position of the pulse can assume an infinity of different timing states (the signal vary continuously) and hence an analog modulation is realised in PPM. On the contrary if the signal is digitized previously in a series of discrete states, the pulse at the output will have discrete timing interval (not continuosly). Then a digital modulation is obtained. If the signal is analog, but the modulator is digital, we will have again a number of finite state in output timing, and the PPM will be digital. To be noted that, if the number of steps in the digital modulator, is higher then the dinamic range required, the performance of the digital and analog PPM will be exactly the same. Cecking the front of the pulse of PPM with a digital oscilloscope capable of jitter measurament, we will see immediately if the position of the pulses will be continuosly variable or a number of discrete steps will be presented. We can then consider analog and digital PPM physically different.
PPM (Pulse Position Modulation) is used in digital communication systems to encode information by varying the position of the pulses in a periodic signal. PWM (Pulse Width Modulation) is commonly used in controlling the power delivered to electronic devices like motors, LEDs, and amplifiers by varying the width of the pulses in a periodic signal.
PAM-pulse Amplitude Modulation It encodes information in the amplitude of a sequence of signal pulses. PPM-Pulse Position modulation PWM-Pulse Width Modulation.It results in variation of average waveform.
100 ppm is worse than 50 ppm. The higher the ppm value, the more concentrated the substance is in the solution. In this case, a concentration of 100 ppm is twice as much as 50 ppm.
ppm
Zn < O.6 ppm Fe < 4.5 ppm Mn < 2.0 ppm Cu < 0.2 ppm
115 ppm is 0.0115%.
0.110 ppm = 0.000011%