Delta RMC151 User Manual download pdf (Page 82)

RMC70/150 and RMCTools User Manual

modules use 16-bit Analog-to-Digital converters. The RMC150 A module uses 12-bit

Analog-to-Digital converters.

The effective resolution of the Analog-to-Digital converted signal is increased by the

following items:

1. Oversampling

The AA, A2, AP2, H, and G

analog-to-digital converters are read eight times

per sample, increasing the effective resolution of the Analog-to-Digital

converted signal. For example, the eight times oversampling causes a 16-

bit input's effective resolution to be 19 bits (one part in 524,288) over the

full ±10V range.

The Universal I/O module's analog inputs are sampled at 60kHz, which is a

minimum of 15 times oversampling.

2. Input Range Gain

Choosing the ±5V or 4-20mA ranges on the RMC150 H or G

modules

changes the gain of the analog input, increasing the resolution over the

requested range.

Due to the factors listed above, the effective resolution of the RMC analog inputs is

as shown in the table below.

Module

±10V

±5V

4-20mA

AA, A2,

AP2

38.1µV

.15µA

Analog

(H)

38.1µV

19.1µV

.076µA

Analog

(G)

38.1µV

.15µA

Analog

(A)

610µV

305µV

.221µA

Universal

I/O

38.1µV

.15µA

Note:

Typically, noise on the analog signals will exceed these small resolution values, and

will have a larger impact on system performance.

• Quadrature

Quadrature encoder resolution is specified in pulses (also called lines) per revolution

on rotary encoders or pulses per inch (or meter) on linear encoders. The RMC

quadrature input will decode the pulses to generate four counts per pulse. So the

internal resolution on the RMC will be four times the resolution of the encoder given in

pulses. Encoders with 2000 pulses (or 8000 counts) per turn are common. The

maximum quadrature encoder frequency is limited to 8,000,000 counts per second for

the RMC70 and 4,000,000 counts per second for the RMC150.

Delta recommends that the quadrature Counts value should not exceed 24 bits

(16,777,216). See the Exceeding 24 Bits section below.

• Resolver

The RMC150 Resolver module can be configured for 14 or 16 bits per revolution. One

revolution of the resolver will always consist of 65,536 counts on the RMC, regardless

of the resolver resolution parameter. With 16-bit resolution, the counts will increment

by one; with 14-bit resolution the counts will increment by four.

Exceeding 24 Bits

The quadrature and SSI inputs can handle Counts values up to 32 bits. However, Delta

recommends that you design your system and programming such that the quadrature

and SSI Counts value do not exceed 24 bits (16,777,216). The RMC can still interface

62 Delta Computer Systems, Inc.

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