COUNTS

This field holds a raw, non-scaled reading from the transducer. The exact meaning of this field depends on the type of transducer used. It is useful to know the counts in order to set up or verify your Scale and Offset settings. For pressure axes, this field is renamed COUNTS A. For force axes, there are two counts fields, COUNTS A and COUNTS B, corresponding to the first and second input channels. Refer to the appropriate section below for the type of feedback transducer(s) you are using:

Magnetostrictive Displacement Transducers (MDT)

The counts represent the number of 120MHz time periods that have passed either between the Start and Stop return pulses for a Start/Stop MDT or from the rising to falling edges of a PWM MDT. Counts will read 0 when the MDT does not return counts. The actual distance from the end of the rod to the magnet is found by multiplying the counts by the gradient value of the MDT. Therefore, to translate from counts to distance, use the following formulas:

Gradient in msec/in:

$image\ebx_2064089720.gif$

Example: An MDT has a gradient of 9.153 msec/in. The counts read 6000. The following equation finds the position:

$image\ebx_1015944484.gif$

$image\ebx_-1074374580.gif$

Gradient in m/sec:

$image\ebx_1879947501.gif$

Example: An MDT has a gradient of 2845.06 m/sec. The counts read 6000. The following equation finds the position:

$image\ebx_1074109867.gif$

$image\ebx_1218482169.gif$

Synchronous Serial Interface (SSI)

The counts are equal to the counts returned from the SSI interface. That is, SSI transducers return a digital count value. The resolution of the counts is defined for the particular SSI device. Therefore, to translate from counts to distance, use the following formula:

$image\ebx_-544686486.gif$

For linear devices, the resolution will be a unit of linear measure, such as 5um. For rotational devices, the resolution will be in degrees or fractions of a revolution.

Example 1: An SSI has a resolution of 5 um per count. The counts read 6000. The following equation finds the position:

$image\ebx_1861524207.gif$

Example 2: A single-turn rotary absolute encoder with SSI feedback has 8192 counts per revolution. The counts read 6000. The following equation converts the counts to degrees from top-dead-center:

$image\ebx_-1873870274.gif$

Quadrature

For quadrature devices, the counts increase by one each time an A or B quadrature input toggles such that the phase of A leads B. The counts decrease by one each time an A or B quadrature input toggles such that phase of B leads A. The counts are set to zero whenever a position is set by a Zero Position or Offset Positions command, but are otherwise relative.

Analog

The counts used for analog transducers are defined differently depending on the input range and quantity type of the channel. The input ranges include 0-10V, ±10V, 0-5V, ±5V, and 4-20mA. Quantity types include position, velocity, pressure, and force. Pressure, force, and velocity counts are signed 16-bit numbers, which range from 32,768 to 32,767, but position counts are unsigned 16-bit numbers, which range from 0 to 65,535. Therefore, the charts below treat position counts differently.

There are three error conditions that can be triggered from the counts. These are described below:

No Transducer
This condition occurs when the value read from the transducer is below a minimum value. The minimum value depends on the input range and quantity type, and is shown in the charts below. When this condition is detected, the No Transducer status bit is set, and the axis will be halted.
Transducer Overflow
This condition occurs when the analog reading is at its maximum value, which will be 32,767 for all analog axes except analog position inputs, in which case it will be 65,535. When this condition is detected, the Transducer Overflow status bit will be set. However, the axis may or may not be halted depending on the configuration of the Auto Stop parameter for this axis.
Transducer Noise
This condition occurs only for analog Position Control axes. For these axes, it is triggered when the transducer feedback jumps by more than 100 position units per millisecond, for at least six control loops in a row. The reason the value of 100 units/ms was chosen is that a Position Control can only be commanded in the RMC to move 65,535 units/s, and therefore 64 units/ms. So a feedback speed above 100 units/ms is deemed to be noise. When this condition is detected, the Transducer Noise status bit is set, and the axis is may or may not halt depending on the configuration of the Auto Stop parameter.

The tables below list the counts given for the minimum input readings, plus the over- and under-range readings for each input range.

0 to 10V
	Pressure, Force, Velocity		Position
	Input	Counts	Input	Counts
	>10.08V	32,767*	>10.07V	65,535*
	10.00V	32,500	10.00V	65,100
	0.00V	0	0.00V	100
	<-0.50V	<-1,625**	<-0.02V	0**
-10 to 10V
	Pressure, Force, Velocity		Position
	Input	Counts	Input	Counts
	>10.08V	32,767*	>10.09V	65,535*
	10.00V	32,500	10.00V	65,250
	0.00V	0	0.00V	32,750
	-10.00V	-32,500	-10.00V	250
	<-10.08V	<32,768**	<-10.08V	0**
0 to 5V
	Pressure, Force, Velocity		Position
	Input	Counts	Input	Counts
	>+5.04V	32,767*	>5.03V	65,535*
	5.00V	32,500	5.00V	65,100
	0.00V	0	0.00V	100
	<-0.25V	<-1,625**	<-0.01V	0**
-5 to 5V
	Pressure, Force, Velocity		Position
	Input	Counts	Input	Counts
	>5.04V	32,767*	>5.04V	65,535*
	5.00V	32,500	5.00V	65,250
	0.00V	0	0.00V	32,750
	-5.00V	-32,500	-5.00V	250
	<-5.04V	-32,768**	<-5.04V	0**
4 to 20mA
	Pressure, Force, Velocity		Position
	Input	Counts	Input	Counts
	>20.16mA	32,767*	>20.13mA	65,535*
	20.00mA	32,500	20.00mA	65,100
	4.00mA	6500	4.00mA	13,100
	<3.60mA	<5850**	<3.60mA	11,800**

* Counts in this range will cause the Transducer Overflow bit to be set in the Status Word, as described above.

** Counts in this range will cause the No Transducer bit to be set in the Status Word, as described above.