MOOGP-I Servoamplifier G122-829A001

 It leaves input 1 available for command. See 6.2 below.

 It has inverting (negative) and non-inverting (positive) inputs.

 It has zero and gain adjustment pots. This enables a signal 

that does not go to zero volts and has less span than the 

command, to be scaled up to the command. While this is 

not essential, it helps when setting up and trouble-shooting.

 There is a front panel test point for the zeroed and amplified 

signal. This is very convenient (essential) for setting up and 

trouble-shooting.

 There is the option of a plug-in resistor, R16, to give a 

feedback derivative (lead or D) in the output of the feedback 

amplifier.

 It can be set up for a current input by connecting a 240 Ohm 

resistor between terminals 17 and 18 with the 4-20mA 

switch ([SW1:4]).

Default

The feedback amplifier default set-up is 4-20mA flowing into 

terminal 18 and out of terminal 17, producing an output of 

0 to -10V. Reversing the terminals, and hence the current flow, 

will not result in a 0 to +10V output. The feedback zero must 

be adjusted for this arrangement.

Adjusting feedback amp for 4-20mA input and 

0 to -10V output

 Set the feedback gain to minimum (fully counter clockwise). 

The trimpot has 15 turns and will click when minimum is 

reached.

 Connect terminal 17 to terminal 26 (ground).

 Connect the positive of a variable DC power supply to 

terminal 18 and the negative to terminal 26.

 Connect a digital multimeter (DMM), on DC Volts, between 

the front panel feedback amp and ground test points.

 Set the variable supply to 0.96V.

 Adjust the feedback amp zero trimpot until the DMM reads 

0.00V.

 Set the variable supply to 4.80V.

 Adjust the feedback gain trimpot until the DMM reads 

-10.00V.

 Set the variable supply to 0.96V again and check the 

feedback test point is still 0.00V. Trim if necessary and check 

the 4.80V setting again

6.2 Input 1

An input to the error amplifier: This input is ±10V 

non-inverting and has two important features:

 It has a scale pot on its input that enables large inputs to be 

scaled down to match smaller signals on other inputs. Scale 

range is 10 to 100%. Set fully clockwise (FCW), an input of 

100V can match a 10V signal on the other inputs. Note that 

the maximum permissable input voltage is ±95V.

 It has a switch selectable (SW4:2) lag of 55mS that can be 

used to remove transients from the input signal that could 

cause unwanted rapid movement in the output.

Input 1 is well suited to be a command because of these two 

features. If input 1 is used for feedback, be sure the lag is 

switched off. Input resistance after the scale pot is 94k Ohms.

6.3 Input 2

An input to the error amplifier: This input is differential, with 

non-inverting and inverting inputs. It is switch selectable (SW5) 

between 4-20mA and ±10V. The 4-20mA converter produces 

0 to +10V for 4 to 20mA input to terminal 7. R34 connects 

from the output of the amplifier to the input of the error amp. 

It is a plug-in resistor with a default value of 100k Ohms, 

giving a nominal ±10V input signal range when V is selected. 

Input 2 is suitable for command or feedback. R34 can be 

increased to give a larger input range.

Terminal 8, the inverting input, can be connected to ground 

with SW6:1.

6.4 Input 3

An input to the output summing and limiting amplifier via a 

plug-in resistor, R33. A typical use for this input is command 

feed forward or closing the outer loop of a three stage valve. 

With R33 at 10k Ohm, a ±10V input will produce ±100% valve 

drive. Increasing R33 reduces the valve drive.

The summing amp gain can be changed with plug-in resistor 

R27. This is useful if input 3 is being used to close the outer 

loop of a three stage valve.

7 Output configuration

Select the output to match the input requirements of the valve 

(SW2).

 When voltage (V) is selected, ±10V is available into a 

minimum load of 200 Ohm.

 When current (I) is selected, the current level switches 

(SW1:X) enable ±5 to ±100mA to be selected. The switch 

selections sum, so, if for instance 45mA is required, select 

30,10 and 5. The output can drive all known Moog valves 

up to ±100mA. The maximum load at I (Amp) output is:

 RL max = 11V – 39 Ohm

I (Amp)

eg. at 50mA RL max is 181 Ohm

 When 4-20mA is selected, the output V/I switches must be 

in I and the output current SW1 must have switch 3 selected 

for 20mA. Maximum load for 4-20mA output is 500 Ohm.

The output amplifier is limited to approximately 105% of the 

selected full scale output. If both the proportional and 

integrator stages are saturated, the output will not be twice 

the selected full scale but still only 105% of full scale.

8 Step push button

The step push button (SW3) injects -50% valve drive 

disturbance into the output. When released, the valve drive 

reverts to its original level. This feature is useful for closed loop 

gain optimisation.

9 P-I selection

For position closed loops, initially select only P (SW6:2). For