- 上一篇：顺流式填充床减阻英文文献和中文翻译
- 下一篇：冷却系统研究及注射模设计英文文献和中文翻译
4. SET UP.
4.0 Introduction
When the positioner/actuator combination is installed in its application, set up the control adjustments if necessary. For most applications, it is likely that the factory settings will be satisfactory – the low and high current points are set to give 0-90 degree movement in response to a 4-20mA signal, the flow regulators are set for maximum travel speed, and the proportional gain and damping settings adjusted for a good level of sensitivity and smoothness suitable for most applications. The jumper is set in the “off” position to give linear characteristics with travel extrapolated beyond the low and high current settings. If you need to change the settings, read the following section carefully.
4.1 Setting Travel Speed.
Set the travel speed using the exhaust flow adjuster screws (see Figure 4.). This
only applies if you want to reduce the speed from its supplied maximum factory
setting.
4.2 Setting Optional Limit Switch Cams.
Optional limit switch cams are factory set to give end-of-travel switching with one
switch each end. The switching can be set to occur anywhere in the travel range for each switch, by relaxing the cam clamp screw and rotating the cam to position. Set the lower cam first. Take care to avoid the clamp section of a cam striking a switch at any point in the actuator's travel. Two possible types of coupling require slightly different approaches to setting:
4.2.1 Moulded coupling cams, shown in figure 6a, can be adjusted using light pressure to rotate in 1 degree increments. Adjust the lower cam first using a screwdriver to lever against special pegs moulded into the carrier plate or use finger pressure. Secondly move the upper cam using finger pressure only. Graduated marks on the top of the coupling are provided to gauge the position of the actuator with the lid removed. This can be lined up with an arrow marked on the servo valve lid.
4.2.2 Metal coupling cams are adjusted by releasing the screw shown in figure 6b, moving to desired position and re tightening. Set the lever cam first. Ensure the clamp section of the cam does not strike a switch at any part in the actuator's travel.
4.3 Overview – Electronic Settings.
The EL digital positioner circuit can operate to give actuator position accurately proportional to input current, or it can operate as a non-linear device accurately following one of a number of fast open, or slow open, exponential curves. Linear or non-linear, it can easily be calibrated to scale its operating line, or curve, between any two user defined points in its operating range. The positioner circuit is powered entirely from the 4-20mA input signal. It is tuned and calibrated by simple and quick operation of its three push buttons, with red LED (light emitting diode) indication of the selected parameter. The positioner can also calibrate itself automatically to the actuator or valve endstops. The actuator dynamic response can be optimised by simple adjustment of the positioner circuit proportional gain and damping variables. All tuning and calibration data is stored digitally, and is retained in non-volatile memory, so that the positioner powers up with all the same settings it had when last powered down.
The positioner may be operated either as a linear or non-linear device. Non-linear operation is enabled by fitting a jumper link to the positioner with the positioner (and position retransmit if fitted) powered down (i.e. input current at 0 mA). When the positioner is powered up with the link “on” (see figure 6 for its position), it will then operate as a non-linear device for as long as it remains powered up. Conversely, when the positioner is powered up with the link “off”, it will operate as a linear device as long as it remains powered up. Changing the link from “on” to “off” or vice-versa while the circuit remains powered up will not cause a change from non-linear to linear operation – the position of the link is only effective during power up.