.TH E1432_SET_INPUT_OFFSET 3 E1432
.SH NAME
.nf
e1432_set_input_offset \- Set input offset voltage
e1432_get_input_offset \- Get current input offset voltage
.fi
.IX e1432_set_input_offset(3) 3
.IX e1432_get_input_offset(3) 3
.SH SYNOPSIS
.cS
SHORTSIZ16 e1432_set_input_offset(E1432ID hw, SHORTSIZ16 ID,
                                  FLOATSIZ32 input_offset)
SHORTSIZ16 e1432_get_input_offset(E1432ID hw, SHORTSIZ16 ID,
                                  FLOATSIZ32 *input_offset)
.cE
.SH DESCRIPTION
\fIe1432_set_input_offset\fR sets the input offset voltage, of a
single channel or group of channels \fIID\fR, to the value given in
\fIinput_offset\fR.

\fIe1432_get_input_offset\fR returns the current value of the input
offset voltage, of a single channel or group of channels \fIID\fR,
into a memory location pointed to by \fIinput_offset\fR.

\fIhw\fR must be the result of a successful call to
\fIe1432_assign_channel_numbers\fR, and specifies the group of
hardware to talk to.

\fIID\fR is either the ID of a group of channels that was obtained
with a call to \fIe1432_create_channel_group\fR, or the ID of a single
channel.

\fIinput_offset\fR is the desired input offset in volts.  This voltage
is subtracted from the input signal, and can be used to remove a
constant DC level from an input signal.  This can be used instead of
AC coupling if the signal's DC level is known ahead of time, thus
avoiding AC filter settling times.  It can also be used in addition to
AC coupling, to help extend the range of the AC coupling filter and to
help the AC coupling filter settle more quickly.

The input offset voltage is used only for input channels - source and
tach channels do not have this feature.

The input offset voltage is only controllable on E1433 196 kHz input
channels.  E1432 51.2 kHz input channels do not have hardware to
implement this feature.  Any attempt to set the input offset voltage
of an E1432 input channel will generate an error.  However,
\fIe1432_get_input_offset\fR will return 0.0 for E1432 input channels.

The input offset voltage is settable over a continuous range of 0
volts to 20 volts.  The resolution is approximately 5 mV.  Negative
voltages are not valid.  The E1433 196 kHz input hardware will clip
the input signal if the signal exceeds about 21 volts, regardless of
the input offset voltage setting.  Unfortunately, this clipping is not
detected by the hardware, so there is no overload indication in this
case.

The input offset voltage is normally only useful when the input mode
is voltage or ICP mode (see \fIe1432_set_input_mode\fR).  In
microphone or charge input modes, there is typically no offset that
needs to be subtracted out.  This function will still "work" when the
input mode is microphone or charge mode, however the voltage that is
subtracted out will not necessarily match the parameter that is
applied, due to scaling performed by the break-out box.  Therefore,
it's typically best to set the input offset voltage to zero in
microphone or charge modes.

.SH "RESET VALUE"
After a reset, input channels have the \fIinput_offset\fR set to 0
volts.
.SH "RETURN VALUE"
Return 0 if successful, a (negative) error number otherwise.
.SH "SEE ALSO"
.na
e1432_get_input_offset_limits, e1432_set_coupling, e1432_set_input_mode
.ad
