Acromag SP33 0700 Series, User Manual, Page: 30 / 37

Acromag, Inc. Tel: 248-295-0880 - 30 - https://www.acromag.com
Model SP33X-0700
4-Wire DC I/V Signal Splitter w/USB
Input...continued
Analog to Digital Converter (A/D): Input utilizes a 24-bit,

-

A/D converter, with
only the first 16-bits used. Its signal is then normalized to a bipolar range count of
±25000 to simplify I/O scaling (see Resolution below).
Sampling Rate (A/D): Input is sampled at a variable rate with input filter selection as
follows:
A/D SAMPLING RATE (SAMPLES/SECOND) PER INPUT FILTER
NONE
LOW MED HIGH
214.65sps 53.6625sps 13.42sps 1.6775sps
Input Impedance: SP336 24.9

minimum at TB1 (current-shunt), and 15M

minimum at TB2 (no resistor divider is present at TB2 which is directly connects to
ADC); SP337 15M

minimum at TB1 (no resistor divider), and 1084.6KΩ at TB2 (a
12.5:1 resistive divider is present at TB2); SP338 1054.2K

at TB1 (an 18.758:1
resistive divider is present at TB 1), and 1003.36KΩ at TB2 (a 187.194:1 resistive
divider is present at TB2).
Input Overvoltage Protection: Inputs include Bipolar Transient Voltage Suppressers
(TVS) with 5.6V clamp level typical (SP336), 14V working, and 18V clamp level typical
and 14V working (SP337), and 220V working voltage typical (SP338). All inputs to
ADC also include differential input diode clamping, capacitive filtering, and series
resistance.
Input Filter: Normal mode RC filtering, plus digital filtering, optimized and fixed per
input range and filter selection within the

-

ADC. See Normal Mode Noise
Rejection and Output Response Time.
Noise Rejection (Common Mode): Varies with input and filter selection between no
filter and high filter and assumes a 100

input unbalance as follows (typical):
MODEL NO FILTER HIGH FILTER
SP336 105dB 139dB
SP337 83dB 133dB
SP338 75dB 91dB
Noise Rejection (Normal Mode): Varies with input and input filter selection. Table
below indicates the typical rejection at 60Hz for each input and input filter selection.
Note that at the medium and high input filter settings, the A/D converter adds 80dB
minimum of rejection for frequencies between 49Hz and 61Hz.
IN RANGE (±MAX)
TYPICAL 60Hz REJECTION PER INPUT & INPUT FILTER
NONE LOW MED HIGH
SP336 TB1 (±20mA) 4.2dB 10dB > 80dB > 80dB
SP336 TB2 (±0.5V) 7dB 25dB > 80dB > 80dB
SP337 TB1 (±1V) 1.1dB 11dB > 80dB > 80dB
SP337 TB2 (±10V) 21dB 37dB > 80dB > 80dB
SP338 TB1 (±15V) 17dB 34dB > 80dB > 80dB
SP338 TB2 (±150V) 15dB 31dB > 80dB > 80dB