3595-1Q1 - 20 Channel Analogue Reed Relay IMP Replacement of 3595-1H IMP

The 3595-1Q1 is an enhanced version of the 3595-1C1, which includes 3 and 4 terminal resistance and RTD measurement facilities organised in a similar way to the original 3595-1H IMP. All 20 channels are available to use in pairs for the 3 and 4 wire measurement modes.

The channels of the 3595-1Q1 are fully programmable and so each 3 or 4 wire measurement takes up2 channels but leaves the rest available for other 3595-1C measurement modes are programmed using the same codes as a 3595-1H. The connector wiring for the 3 and 4 terminal resistance modes differs a little from the 3595-1H, but otherwise the 3595-1Q is compatible with the measurement modes of the 3595-1H analogue channels.


  • Compatible Communications with 3595 series.
  • Compatible enclosure and connector blocks.
  • Thermocouple, resistance, RTD, voltage and current measurements in rugged enclosure.
  • 20 Channels per Module – precision reed relay isolation. Individually programmable.
  • Precision 3 and 4 wire resistance and RTD measurements. (3595-1Q1)
  • Enhanced 14 to 19/20 bit resolution. 100 to 10 measurements per second.
  • Enclosed connector blocks. Dual sensor accurate Cold Junction Compensation.
  • Thermocouple health monitoring Temperatures in °C or °F unit.


Current Measurement

Number of channels / module: 20/10

Number of poles / channel: 3/6

Connector type input channels: Standard 3595 series, Isothermal Enclosure, Screw Terminals.

Measurement modes: V DC (mV, DC, uVDC) Thermocouple CJC temperature, Sensor health.

Thermocouple types: K,J,T,R,S,E,B,N

Thermocouple compensation: Dual sensors

3595-1Q1 only: 3&4 wire resistance, 3&4 wire PT100.

Sensitivity ( 100R shunt fitted): <10nA

Accuracy as for voltage ranges + shunt accuracy.

A-D Converter

Interference Rejection

Measurement resolutions supported:

  • 19/20 bits at 9 measurements/s
  • 18/19 bits at 20 measurements/s
  • 17 bits at 30 measurements/s
  • 17 bits at 40 measurements/s
  • 15 bits at 80 measurements/s
  • 14 bits at 100 measurements/s
  • Number of bits includes sign counted as 1 bit.

50 Hz Mains frequency interference rejection is provided by 17 and 20 bit modes.

60 Hz mains interference rejection is provided by 17,19 and 20 bit modes.

Higher Measurement rates  possible by disabling drift correct measurements.

AC 50/60Hz

Common mode rejection ratio channel group: <0.1uV/V

Single channel common mode rejection ratio: <1uV/V

Series mode rejection ratio 50 or 60 Hz +/- 0.05%: <1mv/V

Applies to 18,19,20 bit measurements.

DC channel common mode rejection ratio: <0.1uV/V

Maximum voltages operating:

Max. voltage between (+) and (-) inputs, same channel: +-12V

Maximum voltage between any two terminals: 200V

Note: reed scanners are not suitable for direct connection to power circuits.

Voltage measuring mode

Overload Protection

Input voltage ranges:            


+2.0V >-2.0V

+200mV >-200mV

+30mV >-30mV

Automatic range selection is supported.

DC measurement accuracy +/- 0.015% of reading + 0.01% of range + 4uV

Temperature coefficients DC voltage: 25ppm rdg + 0.1uV/o C

Measurement sensitivity 30mV range 18 bits: <0.25uV

Additional error at 80 & 100/sec mode 0.03% of range.

Channel overload protection: Passive 50V Continuous


Power Requirement

For protection against transients and ground loops.

Isolation test voltage IMP to IMP or to SNET: Tested at 500V

Connector: Via SNET cable

Voltage: 11 to 48V

Current: <100mA at 12V, <50mA at 24V

Thermocouple Measurement Accuracy

Internal Cold junciton compensation errors included: (External compensation is also available)


Type Range Accuracy
K -100 to 500 0.05°C
  500 to 1200 0.7
  1200 to 1600 3.0
J -50 to 360 0.5
  360 to 800 0.7
T -150 to 400 0.5
R 0 to 1600 2.0
S 0 to 1700 2.2
E -50 to 290 0.7
  290 to 1000 1.0
B 200 to 1600 4.5
N -200 to 1600 1.3
  -100 to 580 1.1.5
  80 to 1300 1.3

SNET Interface: SNET standard compatible

Status LED’s: 4

Function: Power, Communication, ADC fault, Calibration error

Safety: EN61010-1:2010, EN61010-2-30:2010

EMC: EN55011:2009, EN 61326-2-1:2006

Case size: 435*215*34.5mm

Protrusion of cable boots: 45mm

Weight: 3.23kg

Operating Temperature Range: -20 to 70 °C

Relative Humidity(non condensing): 85% at 40°C

Vibration: 1g 10hz to 400Hz in 3 planes.

Programming storage: Secure flash memory

Calibration temperature is 21°C

Displayed sensitivity: <0.1oC

Thermocouple Health Monitoring automatic by resistance measurement sequence.