Anyone who has ever listened to AM and FM radio stations during a
thunderstorm knows that FM (frequency modulation) provides clearer signals than
AM (amplitute modulation). That's because electrical noise affects amplitude
more directly than it affects frequency. Your ear interprets the noise as
crackling "static." Your stepper motor interprets it as random steps, which show
up as "jitter" in the output position.
Pulse-width modulation (PWM) is a sophisticated form of frequency modulation,
and its noise suppression makes it especially useful for applications in motion
control, broadcasting, and communications.
Our HPWM 02U analog output board provides two PWM output channels with 16-bit
resolution. Each of the two PWM output channels is isolated to 2,500VDC.
Continuing your protection against electrical noise, all 8 digital inputs are
also isolated to 2,500VDC. Each digital input can also act as a counter.
Additional protection is provided by 8 SPDT output relays with dielectric
strengths of 1,500 Vrms (coil to contact) or 1,000 Vrms between open contacts.
Relays 0 and 1 provide both NO and NC outputs, while relays 2 through 7 are set
to NO or NC by individual jumpers. A single jumper sets all output relays to
either open of last state on hot resets. All relays have operating times and
release times of 5ms maximum