MTS FlexTest Models 200 - Manual (Page 160)

MTS FlexTest® Models 40/60/100/200 Controller Hardware
Model 494.16 VD/DUC Mezzanine Card
Mezzanine Cards 160
Model 494.16 VD/DUC Mezzanine Card
About the Model 494.16 VD/DUC Card
The Model 494.16 VD/DUC card combines a valve driver (VD) and a digital
universal conditioner (DUC) on a single mezzanine card. You can install this
card in one of the four slots in the Model 494.40 I/O Carrier board.
2-stage valve
applications
The valve driver can drive single or dual 2-stage servovalves. With the 2-
stage configuration, you can use the DUC portion of this card for the “active
mode” feedback signal or for an auxiliary input signal.
3-stage valve
applications
The valve driver can drive one 3-stage servovalve. With the 3-stage
configuration, the DUC portion of this card is reserved for the inner-loop
feedback signal from the valve-spool LVDT.
Model 494.16 Valve Driver Features
Valve outputs
The valve driver on the Model 494.16 Card includes two valve outputs that
provide identical drive signals. With two outputs, each valve coil on a single
servovalve can be driven with a separate current source. You can also use the
two outputs to drive dual two-stage servovalves.
Valve-driver features • Each valve-driver output has programmable full-scale current.
• Each valve-driver output includes a programmable dither signal to help
prevent servovalve silting and to overcome static friction.
• Each valve-driver output includes a valve balance control. This signal is
a DC offset added to the servovalve command to compensate for any
mechanical unbalance in the servovalve.
Safety features
The valve-driver circuit includes features that help prevent valve movement
during startup or loss of power.
• When you initially apply power, a software switch connects the valve
outputs to ground until control is established.
• During interlock conditions (such as loss of DC chassis power) a
software switch shorts the valve outputs to help keep the valve from
moving.
• A set of diodes on the output helps protect the control circuit from
voltage spikes generated by the valve coil.