Measurement Computing StrainBook/616 - Manual (Page 12)

1-2 Introduction 929494 StrainBook/616
WaveView supports up to 64 channels of strain, voltage, or sound/vibration input. For applications beyond
64 channels, or for custom applications, comprehensive drivers are included for Windows languages,
LabVIEW®, and DASYLab®.
StrainBook/616 includes a 1 MHz A/D converter that can scan all selected channels at 1µs per channel and
continuously transmit acquired data to the PC in real time. However, when the simultaneous sample and
hold option (SSH) is turned on, amplifiers ensure that all channels are measured within 100 ns of each
other. The amount of data acquired is only limited by the storage capacity of the host PC. If the channels
are in SSH mode the maximum sample rate is further reduced by one sample. This is to give the SSH
amplifier time to sample. This means that each of the 8 StrainBook channels (when in SSH) can be
scanned at 111 kHz. This equals 1 MHz divided by 9; where the 9 is from the 8 channels plus the 1
additional sample rate reduction and the 1 MHz is from the A/D converter processing speed.
When all 8 channels of the StrainBook/616 are configured the maximum sample rate per channel is
125 kHz. This maximum rate per channel is derived by dividing the 1 MHz [from the A/D converter] by
the number of channels. Thus, when 64 channels of strain are configured the rate is 15.6 kHz per channel.
StrainBook/616 supports a wide range of bridge values configured for full, half, and quarter bridge
configurations. Excitation with remote sensing is supplied from an internal regulator, eliminating the need
for an external voltage source. The unit includes wide gain ranges and filter selection which make it an
excellent general purpose or high gain amplifier for other transducer inputs.
Up to 8 input signals attach to the unit, each via a DB9 connector on the front panel. Each channel has an
independent gain stage. The stage is software programmable in more than 50 steps from 1 to 20,000 to
provide optimal gain for any strain application. The excitation source is accurate to ±5 mV with very low
drift over time.
The dual excitation sources are set through software to 0.5, 1, 2, 5, or 10 volt excitation and can be used in
either a standard or 6-wire Kelvin configuration. Each channel is individually current limited to 85 mA to
protect against accidental short circuits.
Both high-AC coupling and low-pass noise rejection filtering can be enabled through software. Two 4-
pole Butterworth filters factory-set to corner frequencies of 10 Hz or 1 kHz pass can be selected. The
filters can be modified over a range of 2 Hz to 20 Hz by inserting a user-supplied resistor pack.
Unlike most strain instruments that make use of a single fixed configuration, both the StrainBook/616 and
the WBK16 option allow multiple bridge-configurations to be pre-configured on a user-installed header.
Once installed, each configuration can be selected via software. In addition, many configurations can be
changed via software. For example, you can change a transducer from full-bridge to quarter-bridge using
software alone, i.e., with no physical alteration to the bridge. Transducer resistance can also be changed
via software.
Each header supports: 2 half-bridge resistors, 3 quarter-bridge values, and 3 shunt-cal values per channel.
Three software-selectable shunt calibration resistors [to be supplied by the customer] are user-installable
for each channel. This allows each channel to be placed into a known imbalance condition to set or verify
channel calibration. Shunt-cal allows a full-scale gain to be set without physically loading the bridge to
capacity.
Bridge balancing is quick and convenient as there are no potentiometers to adjust. Just select “auto-
balance” for the associated channels. Auto-balance removes the static portion of the strain load and auto-
zeros the input to compensate for any input drift.