6ES7321-1BH02-0AA0

Product information

The 6ES7321-1BH02-0AA0 is a Siemens SIMATIC S7-300 digital input module: SM 321, isolated, 16 DI at 24 V DC, with a single 20-pole connection. It carries 16 simultaneously controllable inputs in every mounting position up to 40 °C.

This is the standard 24 V DC input module of the S7-300 range, used to bring field signals — proximity switches, contacts, limit switches and similar — into the controller. Inputs follow the IEC 61131 type 1 characteristic curve, with signal “0” recognised between −30 and +5 V and signal “1” between 13 and 30 V.

Technical specifications

Manufacturer / family	Siemens · SIMATIC S7-300
Product type	SM 321, digital input, isolated
Number of digital inputs	16
Input voltage	24 V DC, rated
Signal “0” range	−30 to +5 V
Signal “1” range	13 to 30 V
Input current at signal “1”	7 mA typical
Input characteristic	IEC 61131, type 1
Load voltage L+	24 V DC (permissible 20.4–28.8 V DC)
Current from backplane bus	Max. 10 mA at 5 V DC
Power loss	3.5 W typical
Connection	1 × 20-pole
Isochronous mode	No

Specifications as published in Siemens product data for this article number. Verify against the nameplate of the unit offered to you.

Lifecycle status

Siemens product data identifies this article number as a spare part. For S7-300 installations still in service, that means replacement input modules come from surplus supply, and the exact article number — not merely “16 DI, 24 V DC” — is what should be matched, since several SM 321 variants share that description with different isolation, diagnostics and connection arrangements.

Typical applications

• Collecting 24 V DC field signals in S7-300 racks — proximity switches, contacts and limit switches
• Rack expansion where additional digital inputs are needed beyond the CPU or existing modules
• Spare-part replacement on existing installations

Application examples describe typical uses of this product type. Suitability for your own installation must be confirmed against your engineering documentation.

Related references

• 6ES7322-1BH01-0AA0 — SM 322 digital output module, 16 DO at 24 V DC, 0.5 A
• 6ES7331-7KF02-0AB0 — SM 331 analog input module, 8 AI
• 6ES7392-1AM00-0AA0 — front connector, 40-pole, screw terminals

Before you order

To confirm a specific unit, please provide the complete ordering code, a nameplate photograph, the quantity required and the delivery destination. Availability, condition, quantity, lead time and commercial terms are confirmed individually after inquiry.

Frequently asked questions

Is this module suitable for 24 V DC signals only?
Yes. The rated input voltage is 24 V DC, with signal “1” recognised from 13 to 30 V and signal “0” from −30 to +5 V.

Does it need an external load voltage?
The module works with the load voltage L+ of 24 V DC (20.4–28.8 V DC), supplied through the rack arrangement.

How many poles does the front connector need?
1 × 20-pole, matching the module’s connection arrangement.

Is it still produced?
Siemens lists it as a spare part. Confirm availability for the specific revision you require.

What is the price and lead time?
Confirmed individually against current availability and quantity.